Deposition of SiN

ABSTRACT

Methods and precursors for forming silicon nitride films are provided. In some embodiments, silicon nitride can be deposited by atomic layer deposition (ALD), such as plasma enhanced ALD. In some embodiments, deposited silicon nitride can be treated with a plasma treatment. The plasma treatment can be a nitrogen plasma treatment. In some embodiments the silicon precursors for depositing the silicon nitride comprise an iodine ligand. The silicon nitride films may have a relatively uniform etch rate for both vertical and the horizontal portions when deposited onto three-dimensional structures such as FinFETS or other types of multiple gate FETs. In some embodiments, various silicon nitride films of the present disclosure have an etch rate of less than half the thermal oxide removal rate with diluted HF (0.5%). In some embodiments, a method for depositing silicon nitride films comprises a multi-step plasma treatment.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/426,593, filed Feb. 7, 2017, which is a continuation of U.S.application Ser. No. 14/855,261, filed Sep. 15, 2015, now issued as U.S.Pat. No. 9,576,792, which claims priority to U.S. ProvisionalApplication No. 62/180,511, filed Jun. 16, 2015, and U.S. ProvisionalApplication No. 62/051,867, filed Sep. 17, 2014, each of which isincorporated herein by reference in its entirety.

BACKGROUND

Field

The present disclosure relates generally to the field of semiconductordevice manufacturing and, more particularly, to low temperaturedeposition of silicon nitride films and precursors for use in depositionof silicon nitride films.

Description of the Related Art

Spacers are widely used in semiconductor manufacturing as structures toprotect against subsequent processing steps. For example, nitridespacers formed beside gate electrodes can be used as a mask to protectunderlying source/drain areas during doping or implanting steps.

As the physical geometry of semiconductor devices shrinks, the gateelectrode spacer becomes smaller and smaller. The spacer width islimited by the nitride thickness that can be deposited conformably overthe dense gate electrodes lines. So the nitride spacer etching processis preferred to have a high ratio of spacer width to nitride layerthickness as deposited.

Current PEALD silicon nitride processes in general suffer fromanisotropic etch behavior when deposited on a three-dimensionalstructure, such as a trench structure. In other words, the filmdeposited on the sidewalls of a trench or fin or another threedimensional feature display inferior film properties as compared to filmon the top region of the feature. The film quality may be sufficient forthe target application on the top of the trench, or on planar regions ofa structured wafer, but not on the sidewalls or other non-horizontal orvertical surfaces.

FIGS. 1A and 1B illustrate a typical example of a silicon nitride film,which could be used in spacer applications. The film was deposited at400° C. using a PEALD process other than those described in the presentapplication. FIG. 1A illustrates the film after it was deposited on athree-dimensional surface but prior to being etched by HF. An etchingprocess was then performed by dipping the workpiece in 0.5% HF for about60 seconds. FIG. 1B illustrates the extent to which vertical portions ofthe silicon nitride film etch to a greater extent than the horizontalportions of the film. The film thicknesses are indicated in nanometers.Structures such as these would not generally survive further processing,such as in a FinFET spacer application.

SUMMARY

In some aspects, atomic layer deposition (ALD) methods of depositingsilicon nitride films are provided. In some embodiments the ALD methodsmay be plasma enhanced ALD methods or thermal ALD methods. The methodsallow for the deposition of silicon nitride films with desirablequalities, such as good step coverage and pattern loading effects, aswell as desirable etch characteristics. According to some embodiments,the silicon nitride films have a relatively uniform etch rate for boththe vertical and the horizontal portions, when deposited onto3-dimensional structures. Such three-dimensional structures may include,for example and without limitation, FinFETS or other types of multiplegate FETs. In some embodiments, various silicon nitride films of thepresent disclosure have an etch rate of less than half the thermal oxideremoval rate of about 2-3 nm per minute with diluted HF (0.5%).

In some embodiments, methods of depositing silicon nitride films on asubstrate in a reaction chamber comprise introducing a vapor phasesilicon reactant to the reaction space such that silicon species adsorbon the substrate surface, removing excess silicon reactant, contactingthe adsorbed silicon species with a reactive species generated by plasmafrom a nitrogen precursor, and removing excess reactive species andreaction by-products. These steps are repeated to achieve a siliconnitride film of the desired thickness.

In some embodiments, the silicon precursor comprises a precursor offormulas (1)-(8) as described herein. In some embodiments the siliconprecursor is selected from the group consisting of HSiI₃, H₂SiI₂, H₃SiI,H₂Si₂I₄, H₄Si₂I₂, and H₅Si₂I. In some embodiments the silicon precursoris H₂SiI₂. The reactive species may comprise, for example, hydrogen,hydrogen atoms, hydrogen plasma, hydrogen radicals, N* radicals, NH*radicals or NH₂* radicals. In some embodiments, the reactive species maycomprise N-containing plasma or a plasma comprising N. In someembodiments, the reactive species may comprise a plasma comprisingN-containing species. In some embodiments the reactive species maycomprise nitrogen atoms and/or N* radicals.

In some embodiments the silicon nitride film is deposited on athree-dimensional structure. In some embodiments the silicon nitridefilm exhibits a step coverage and pattern loading effect of at leastabout 80%. In some embodiments the structure comprises a sidewall andtop regions and the sidewall wet etch rate (WER) of the silicon nitridefilm relative to the top region WER is less than about 3 in 0.5% dHF. Insome embodiments the etch rate of the silicon nitride film is less thanabout 0.4 nm/min in 0.5% aqueous HF.

In some embodiments, methods of depositing a silicon nitride filmcomprise loading a substrate comprising at least one three-dimensionalfeature into a reaction space, contacting the substrate in the reactionspace with a silicon precursor so that silicon species are adsorbed on asurface of the substrate, purging the reaction space of excess siliconprecursor, contacting silicon species adsorbed onto the surface of thesubstrate in the reaction space with a nitrogen precursor, purging thereaction space of excess nitrogen precursor, and repeating the steps toproduce a film of the desired thickness. In some embodiments the filmhas a step coverage of more than about 50% on the three-dimensionalfeature. In some embodiments the wet etch rate of the silicon nitridefilm is less than about 5 nm/min in 5% aqueous HF. In some embodiments aratio of an etch rate of the silicon nitride film in a sidewall of athree-dimensional structure to an etch rate on a top surface is lessthan about 4. In some embodiments the step coverage is at least about80% or about 90%.

In some embodiments, methods of depositing a silicon nitride film on asubstrate comprise, exposing the substrate to a vapor phase siliconprecursor so that silicon species are adsorbed on a surface of thesubstrate, exposing silicon species adsorbed on the surface of thesubstrate to a purge gas and/or a vacuum to remove excess precursor andreaction byproducts from the substrate surface, contacting the adsorbedsilicon species with species generated by a nitrogen plasma, exposingthe substrate to a purge gas and/or a vacuum to remove the species of anitrogen containing plasma and reaction byproducts from the substratesurface and from the proximity of the substrate surface, and repeatingthe steps to produce a film of the desired thickness.

In some embodiments, methods of depositing a silicon nitride film on asubstrate comprise, exposing the substrate to a vapor phase siliconreactant so that silicon species is adsorbed on a surface of thesubstrate, exposing the substrate to a purge gas and/or a vacuum toremove excess precursor and reaction byproducts from the substratesurface, contacting the adsorbed silicon species with a nitrogenprecursor, exposing the substrate to a purge gas and/or a vacuum toremove excess nitrogen precursor and reaction byproducts from thesubstrate surface and from the proximity of the substrate surface, andrepeating the steps to produce a film of the desired thickness.

In some embodiments the silicon precursor comprises iodine or bromine.In some embodiments the film has a step coverage of more than about 50%.In some embodiments the etch rate of the silicon nitride is less thanabout 5 nm/min in 0.5% aqueous HF. In some embodiments a ratio of anetch rate of the silicon nitride on a sidewall of a three-dimensionalstructure to an etch rate on a top surface of the three-dimensionalstructure is less than about 4.

In some aspects, a silicon nitride thin film deposited by a method asdescribed herein can be subject to a plasma treatment. In someembodiments, the plasma treatment comprises exposing the depositedsilicon nitride thin film to plasma generated from nitrogen containinggas free or substantially free of hydrogen species. In some embodiments,the silicon nitride film can be deposited using a plurality of siliconnitride deposition cycles, and the plasma treatment can be applied afterevery deposition cycle, at pre-determined intervals, or after a siliconnitride film of desired thickness is deposited.

In some embodiments, methods of forming a thin film on a substrate in areaction space can include contacting the substrate with a first siliconhalide to provide a first silicon species adsorbed on a surface of thesubstrate, and contacting the substrate comprising the first speciesadsorbed on the surface with a first plasma step to deposit a materialon the substrate. The method may further include conducting a nitrogenplasma treatment, where the nitrogen plasma treatment includescontacting the substrate comprising the material on the surface with asecond plasma formed from a nitrogen containing gas substantially freeof hydrogen-containing species to form the thin film. In someembodiments, the thin film is a silicon nitride film.

In some embodiments, methods of forming a SiN thin film on a substratein a reaction space can include contacting the substrate with a firstsilicon halide to provide a first silicon species adsorbed on a surfaceof the substrate, and contacting the substrate comprising the firstsilicon species adsorbed on the surface with a first plasma including anactivated hydrogen species to thereby deposit SiN. The method mayfurther include conducting a nitrogen plasma treatment to form the SiNthin film, where the nitrogen plasma treatment includes contacting thesubstrate comprising the SiN with a second plasma formed from a nitrogencontaining gas substantially free of hydrogen-containing species. Insome embodiments, a silicon nitride deposition cycle comprisescontacting the substrate with the first silicon precursor and contactingthe first silicon species adsorbed on the surface of the substrate withthe second nitrogen precursor. In some embodiments, the silicon nitrideon the substrate can be contacted with the second plasma after everysilicon nitride deposition cycle, or at various repetitions of thesilicon nitride deposition cycle, such as after every 2, 3, 4, 5, 10,25, 50 or 100 repetitions.

In some embodiments, the first plasma includes at least one of hydrogen,hydrogen atoms, hydrogen plasma, hydrogen radicals, N* radicals, NH*radicals and NH₂* radicals. In some embodiments, the first plasma maycomprise N-containing plasma or a plasma comprising N. In someembodiments, the first plasma may comprise N-containing species. In someembodiments the first plasma may comprise nitrogen atoms and/or N*radicals.

In some embodiments, the first plasma is generated using a first powerand the second plasma is generated using a second power. The secondpower may be greater than the first power. In some embodiments, thesecond power is about 100% to about 900% that of the first power. Insome embodiments, the second power is about 100% to about 200% that ofthe first power.

In some embodiments, second power is less than the first power. In someembodiments, the second power is between about 50% and about 100% thatof the first power. In some embodiments, the first power is about 50 Wto about 600 W. The plasma power of the first power may be about 150 Wto about 250 W. In some embodiments, the second power is about 100 W toabout 1000 W. The second power may be about 150 W to about 300 W.

In some embodiments, contacting the substrate with the first plasma iscarried out for a duration that is greater than the duration of thenitrogen plasma treatment. In some embodiments, the duration of thenitrogen plasma treatment is about 5% to about 75% that of the durationof the first plasma step. The duration of the nitrogen plasma treatmentmay be about 20% to about 50% that of the duration of the first plasmastep.

In some embodiments, methods of depositing the thin film may furtherinclude repeating contacting the substrate with the first precursor,such as a silicon precursor, and contacting the species, such as siliconspecies, adsorbed onto the surface of the substrate with the firstplasma two or more times prior to conducting the nitrogen plasmatreatment. In some embodiments, the nitrogen plasma treatment isconducted after at least 25 repetitions of contacting the substrate withthe first precursor and contacting the species adsorbed onto the surfaceof the substrate with the activated hydrogen species. In someembodiments, the nitrogen plasma treatment is conducted after every 25threpetition. In some embodiments, the nitrogen plasma treatment isconducted after every 50th repetition In some embodiments, the nitrogenplasma treatment is conducted after every 100th repetition.

The SiN film may be formed on a three-dimensional structure. In someembodiments, the structure comprises sidewalls and top regions and wherea ratio of a wet etch rate (WER) of the SiN thin film on the sidewallsto a wet etch rate (WER) of the SiN film on the top regions is less thanabout 1 in 0.5% dHF. In some embodiments, the ratio is from about 0.75to about 1.5, and in some embodiments may be about 0.9 to about 1.1.

In some embodiments, an etch rate ratio of an etch rate of the SiN thinfilm to an etch rate of a thermal silicon oxide film is less than about0.5 in 0.5% aqueous HF.

In some embodiments, contacting the substrate with a silicon halidecomprises iodine. In some embodiments, the silicon halide compriseschlorine. The silicon precursor may be inorganic. In some embodiments,the silicon halide includes SiI₂H₂.

In some aspects, a method of depositing a SiN thin film on a substratein a reaction space can include exposing the substrate to a siliconhalide to provide silicon species adsorbed onto a surface of thesubstrate, and exposing the substrate comprising the silicon speciesadsorbed onto the surface to a first nitrogen-containing plasma, and asecond, different plasma. In some embodiments, the silicon halideincludes iodine. In some embodiments, the silicon halide includeschlorine. In some embodiments, the silicon halide includesoctachlorotrisilane.

In some embodiments, exposing the substrate the firstnitrogen-containing plasma and second other different plasma can includeexposing the substrate to a plasma generated using at least one ofhydrogen gas and nitrogen gas. In some embodiments, exposing thesubstrate to the first nitrogen-containing plasma can include exposingthe silicon species to a plasma generated using both hydrogen gas andnitrogen gas.

In some embodiments, the substrate can be further exposed to a thirdplasma different from at least one of the first plasma and the secondplasma. Two of the first, second and third plasmas may include a plasmagenerated using both hydrogen gas and nitrogen gas, and one of thefirst, second and third plasmas may include a plasma generated usinghydrogen gas.

In some embodiments, the substrate is exposed to the first plasma for afirst duration, the substrate is exposed to the second plasma for asecond duration, and the substrate is exposed to the third plasma for athird duration, and wherein the first duration is greater than thesecond duration. The first duration may be longer than the second. Insome embodiments, the second duration is longer than the third duration.

In some embodiments, each of the first plasma and the third plasma caninclude a plasma generated using both hydrogen gas and nitrogen gas. Insome embodiments, the second plasma can include a plasma generated usinghydrogen gas.

The method of depositing the thin film may include removing excessreactants from the reaction space between the first plasma and thesecond plasma, and removing excess reactants from the reaction spacebetween the second plasma and the third plasma. In some embodiments,removing excess reactants from the reaction space between the firstplasma and the second plasma, and between the second plasma and thethird plasma can each include flowing hydrogen gas. In some embodiments,removing excess reactants from the reaction space a first purge stepbetween the first plasma and the second plasma can include ramping downa flow rate of nitrogen gas. In some embodiments, removing excessreactants from the reaction space between the second plasma and thethird plasma includes flowing hydrogen gas and nitrogen gas. In someembodiments, the removing excess reactants from the reaction spacebetween the second plasma and the third plasma includes ramping up aflow rate of nitrogen gas.

In some aspects, a method of depositing a thin film on a substrate in areaction space can include exposing the substrate to a silicon halidesuch that silicon species adsorb onto a surface of the substrate,exposing the substrate to a first plasma generated usingnitrogen-containing and hydrogen-containing gas, exposing the substrateto a second plasma generated using hydrogen-containing gas, exposing thesubstrate to a third plasma generated using hydrogen-containing gas andnitrogen-containing gas, and repeating exposing the substrate to thesilicon halide, the first plasma, the second plasma and the thirdplasma. In some embodiments, the thin film is a silicon nitride thinfilm. In some embodiments, depositing the thin film is substantiallyfree from additional reactants.

In some embodiments, the first plasma and the third plasma are generatedusing hydrogen gas and nitrogen gas. In some embodiments, the secondplasma is generated using hydrogen gas.

The method of depositing the thin film may include removing excessreactants from the reaction space between exposing the substrate to thefirst plasma and the second plasma, and removing excess reactants fromthe reaction space between exposing the substrate to the second plasmaand the third plasma. In some embodiments, removing excess reactants mayinclude turning off the plasma. In some embodiments, removing excessreactants may include continuing flow of hydrogen gas. The method ofdepositing the thin film may include ramping down flow of nitrogen gasduring removing excess reactants from the reaction space betweenexposing the substrate to the first plasma and the second plasma. Themethod of depositing the thin film may include ramping up flow ofnitrogen gas during removing excess reactants from the reaction spacebetween exposing the substrate to the second plasma and the thirdplasma.

In some aspects, a method of forming a SiN thin film on a substrate in areaction space can include depositing SiN on the substrate using anatomic layer deposition process; and conducting a nitrogen plasmatreatment upon the deposited SiN, where the nitrogen plasma treatmentincludes contacting the substrate comprising the SiN with a nitrogenplasma formed from a nitrogen containing gas substantially free ofhydrogen-containing species. In some embodiments, the atomic layerdeposition process comprises contacting the substrate with a siliconprecursor. In some embodiments, the silicon precursor comprises iodine.

In some embodiments, conducting the nitrogen plasma treatment includescontacting the SiN on the substrate with a plasma substantially free ofhydrogen-containing species.

In some embodiments, the atomic layer deposition process includes aPEALD process, and the PEALD process can include contacting thesubstrate with a silicon halide to provide a first silicon speciesadsorbed on a surface of the substrate, and contacting the substratecomprising the first silicon species adsorbed on the surface with afirst plasma comprising activated hydrogen species. In some embodiments,the silicon halide can include an iodine or chlorine. In someembodiments, the activated hydrogen species can include at least one ofhydrogen, hydrogen atoms, hydrogen plasma, hydrogen radicals, N*radicals, NH* radicals and NH₂* radicals. In some embodiments, the firstplasma may comprise N-containing plasma or a plasma comprising N. Insome embodiments, the first plasma may comprise a plasma comprisingN-containing species. In some embodiments the first plasma may comprisenitrogen atoms and/or N* radicals. In some embodiments, depositing theSiN includes generating the first plasma using a first power and whereinconducting the nitrogen plasma treatment includes generating thenitrogen plasma using a second power, where the second power is greaterthan the first power. In some embodiments, contacting the substrate withthe silicon halide and the first plasma can be repeated two or moretimes prior to conducting the nitrogen plasma treatment.

In some embodiments, the atomic layer deposition process includes athermal ALD process.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the Detailed Description ofthe Preferred Embodiments and from the appended drawings, which aremeant to illustrate and not to limit the invention, and wherein:

FIGS. 1A and 1B illustrate the results of an etching process on asilicon nitride film;

FIG. 2 is a flow chart generally illustrating a method of forming asilicon nitride film by an ALD process in accordance with someembodiments of the present disclosure;

FIG. 3 is a flow chart illustrating a method of forming a siliconnitride thin film by a PEALD process in accordance with some embodimentsof the present disclosure;

FIG. 4 is a flow chart illustrating a method of forming a siliconnitride thin film by a thermal ALD process in accordance with someembodiments of the present disclosure;

FIGS. 5A-5C illustrate field emission scanning electron microscopy(FESEM) images of various silicon nitride films deposited according tosome embodiments of the present disclosure.

FIGS. 6A-6C illustrate FESEM images of the silicon nitride films ofFIGS. 5A-5B after exposure to a 2-minute dHF dip.

FIG. 7 is a flow chart generally illustrating a method of forming asilicon nitride film by a PEALD process in combination with a nitrogenplasma treatment.

FIG. 8 is a flow chart generally illustrating another example of amethod of forming a silicon nitride film by a PEALD process incombination with a nitrogen plasma treatment.

FIG. 9 shows wet etch rate of a silicon nitride film and wet etch rateratio of the silicon nitride film as compared to a thermal silicon oxidefilm, as a function of time dipped in dHF.

FIG. 10 shows an experimental setup for depositing silicon nitride film.

FIG. 11 shows wet etch rate of a silicon nitride film, wet etch rateratio of the silicon nitride film as compared to a thermal silicon oxidefilm, and a thickness of the silicon nitride film as a function ofposition on the substrate.

FIG. 12 are SEM images showing top-down views of silicon nitride filmsand the corresponding schematic showing hydrogen dosage applied to eachsilicon nitride film.

FIG. 13A shows a thickness of silicon nitride film as a function of timedipped in dHF.

FIG. 13B shows wet etch rate ratio of the silicon nitride film of FIG.12A as compared to a thermal silicon oxide film.

FIG. 14A shows a silicon nitride film composition.

FIG. 14B shows wet etch rate ratio performance of the silicon nitridefilm of FIG. 13A as compared to a thermal silicon oxide film.

FIG. 15 shows wet etch rate ratio performance of a horizontal surface ofa silicon nitride film as compared to a horizontal surface of a thermalsilicon oxide film and a vertical surface of the silicon nitride film ascompared to a vertical surface of the thermal silicon oxide film.

FIG. 16 is a flow chart generally illustrating an example of a method offorming a silicon nitride film by a PEALD process where the PEALDprocess includes a multi-step plasma exposure.

FIG. 17 is a flow chart generally illustrating another example of amethod of forming a silicon nitride film by a PEALD process where thePEALD process includes a multi-step plasma exposure.

FIG. 18 is a graph showing gas flow rates and plasma power as a functionof time for an example of a multi-step plasma exposure.

FIG. 19A is a table showing characteristics of an example of a SiN filmdeposited using a PEALD process comprising a multi-step plasma exposure.

FIG. 19B is a table listing some conditions of the multi-step plasmaexposure used in depositing the SiN film of FIG. 19A.

DETAILED DESCRIPTION

Silicon nitride films have a wide variety of applications, as will beapparent to the skilled artisan, such as in planar logic, DRAM, and NANDFlash devices. More specifically, conformal silicon nitride thin filmsthat display uniform etch behavior have a wide variety of applications,both in the semiconductor industry and also outside of the semiconductorindustry. According to some embodiments of the present disclosure,various silicon nitride films and precursors and methods for depositingthose films by atomic layer deposition (ALD) are provided. Importantly,in some embodiments the silicon nitride films have a relatively uniformetch rate for both the vertical and the horizontal portions, whendeposited onto 3-dimensional structures. Such three-dimensionalstructures may include, for example and without limitation, FinFETS orother types of multiple gate FETs. In some embodiments, various siliconnitride films of the present disclosure have an etch rate of less thanhalf the thermal oxide removal rate of about 2-3 nm per minute withdiluted HF (0.5%).

Thin film layers comprising silicon nitride can be deposited byplasma-enhanced atomic layer deposition (PEALD) type processes or bythermal ALD processes. In some embodiments, silicon nitride thin filmsare deposited on a substrate by PEALD. In some embodiments, siliconnitride thin films are deposited on a substrate by a thermal ALDprocess. In some embodiments a silicon nitride thin film is depositedover a three dimensional structure, such as a fin in the formation of afinFET device, and/or in the application of spacer defined doublepatterning (SDDP) and/or spacer defined quadruple patterning (SDQP).

The formula of the silicon nitride is generally referred to herein asSiN for convenience and simplicity. However, the skilled artisan willunderstand that the actual formula of the silicon nitride, representingthe Si:N ratio in the film and excluding hydrogen or other impurities,can be represented as SiN_(x), where x varies from about 0.5 to about2.0, as long as some Si—N bonds are formed. In some cases, x may varyfrom about 0.9 to about 1.7, from about 1.0 to about 1.5, or from about1.2 to about 1.4. In some embodiments silicon nitride is formed where Sihas an oxidation state of +IV and the amount of nitride in the materialmight vary.

ALD-type processes are based on controlled, generally self-limitingsurface reactions. Gas phase reactions are typically avoided bycontacting the substrate alternately and sequentially with thereactants. Vapor phase reactants are separated from each other in thereaction chamber, for example, by removing excess reactants and/orreactant byproducts between reactant pulses. The reactants may beremoved from proximity with the substrate surface with the aid of apurge gas and/or vacuum. In some embodiments excess reactants and/orreactant byproducts are removed from the reaction space by purging, forexample with an inert gas.

The methods presented herein provide for deposition of SiN thin films onsubstrate surfaces. Geometrically challenging applications are alsopossible due to the nature of ALD-type processes. According to someembodiments, ALD-type processes are used to form SiN thin films onsubstrates such as integrated circuit workpieces, and in someembodiments on three-dimensional structures on the substrates. In someembodiments, ALD type processes comprise alternate and sequentialcontact of the substrate with a silicon precursor and a nitrogenprecursor. In some embodiments, a silicon precursor contacts thesubstrate such silicon species adsorb onto the surface of the substrate.In some embodiments, the silicon species may be same as the siliconprecursor, or may be modified in the adsorbing step, such as by losingone or more ligands.

FIG. 2 is a flow chart generally illustrating a silicon nitride ALDdeposition cycle that can be used to deposit a silicon nitride thin filmin accordance with some embodiments. According to certain embodiments, asilicon nitride thin film is formed on a substrate by an ALD-typeprocess comprising multiple silicon nitride deposition cycles, eachsilicon nitride deposition cycle 200 comprising:

(1) contacting a substrate with a silicon precursor 210 such thatsilicon species adsorb on the substrate surface;

(2) contacting the substrate with a nitrogen precursor 220; and

(3) repeating steps 210 and 220 as many times as required to achieve athin film of a desired thickness and composition.

Excess reactants may be removed from the vicinity of the substrate, forexample by purging from the reaction space with an inert gas, after eachcontacting step. The discussion below addresses each of these steps ingreater detail.

PEALD Processes

In some embodiments, plasma enhanced ALD (PEALD) processes are used todeposit SiN films. Briefly, a substrate or workpiece is placed in areaction chamber and subjected to alternately repeated surfacereactions. In some embodiments, thin SiN films are formed by repetitionof a self-limiting ALD cycle. Preferably, for forming SiN films, eachALD cycle comprises at least two distinct phases. The provision andremoval of a reactant from the reaction space may be considered a phase.In a first phase, a first reactant comprising silicon is provided andforms no more than about one monolayer on the substrate surface. Thisreactant is also referred to herein as “the silicon precursor,”“silicon-containing precursor,” or “silicon reactant” and may be, forexample, H₂SiI₂.

In a second phase, a second reactant comprising a reactive species isprovided and may convert adsorbed silicon species to silicon nitride. Insome embodiments the second reactant comprises a nitrogen precursor. Insome embodiments, the reactive species comprises an excited species. Insome embodiments the second reactant comprises a species from a nitrogencontaining plasma. In some embodiments, the second reactant comprisesnitrogen radicals, nitrogen atoms and/or nitrogen plasma. In someembodiments, the second reactant may comprise N-containing plasma or aplasma comprising N. In some embodiments, the second reactant maycomprise a plasma comprising N-containing species. In some embodimentsthe second reactant may comprise nitrogen atoms and/or N* radicals. Thesecond reactant may comprise other species that are not nitrogenprecursors. In some embodiments, the second reactant may comprise aplasma of hydrogen, radicals of hydrogen, or atomic hydrogen in one formor another. In some embodiments, the second reactant may comprise aspecies from a noble gas, such as He, Ne, Ar, Kr, or Xe, preferably Aror He, for example as radicals, in plasma form, or in elemental form.These reactive species from noble gases do not necessarily contributematerial to the deposited film, but can in some circumstances contributeto film growth as well as help in the formation and ignition of plasma.In some embodiments a gas that is used to form a plasma may flowconstantly throughout the deposition process but only be activatedintermittently. In some embodiments, the second reactant does notcomprise a species from a noble gas, such as Ar. Thus, in someembodiments the adsorbed silicon precursor is not contacted with areactive species generated by a plasma from Ar

Additional phases may be added and phases may be removed as desired toadjust the composition of the final film.

One or more of the reactants may be provided with the aid of a carriergas, such as Ar or He. In some embodiments the silicon precursor and thesecond reactant are provided with the aid of a carrier gas.

In some embodiments, two of the phases may overlap, or be combined. Forexample, the silicon precursor and the second reactant may be providedsimultaneously in pulses that partially or completely overlap. Inaddition, although referred to as the first and second phases, and thefirst and second reactants, the order of the phases may be varied, andan ALD cycle may begin with any one of the phases. That is, unlessspecified otherwise, the reactants can be provided in any order, and theprocess may begin with any of the reactants.

As discussed in more detail below, in some embodiments for depositing asilicon nitride film, one or more deposition cycles begin with provisionof the silicon precursor, followed by the second precursor. In otherembodiments deposition may begin with provision of the second precursor,followed by the silicon precursor.

In some embodiments the substrate on which deposition is desired, suchas a semiconductor workpiece, is loaded into a reactor. The reactor maybe part of a cluster tool in which a variety of different processes inthe formation of an integrated circuit are carried out. In someembodiments a flow-type reactor is utilized. In some embodiments ashower head type of reactor is utilized. In some embodiments, a spacedivided reactor is utilized. In some embodiments a high-volumemanufacturing-capable single wafer ALD reactor is used. In otherembodiments a batch reactor comprising multiple substrates is used. Forembodiments in which batch ALD reactors are used, the number ofsubstrates is preferably in the range of 10 to 200, more preferably inthe range of 50 to 150, and most preferably in the range of 100 to 130.

Exemplary single wafer reactors, designed specifically to enhance ALDprocesses, are commercially available from ASM America, Inc. (Phoenix,Ariz.) under the tradenames Pulsar® 2000 and Pulsar® 3000 and ASM JapanK.K (Tokyo, Japan) under the tradename Eagle® XP, XP8 and Dragon®.Exemplary batch ALD reactors, designed specifically to enhance ALDprocesses, are commercially available from and ASM Europe B.V (Almere,Netherlands) under the tradenames A400™ and A412™.

In some embodiments, if necessary, the exposed surfaces of the workpiececan be pretreated to provide reactive sites to react with the firstphase of the ALD process. In some embodiments a separate pretreatmentstep is not required. In some embodiments the substrate is pretreated toprovide a desired surface termination. In some embodiments the substrateis pretreated with plasma.

Excess reactant and reaction byproducts, if any, are removed from thevicinity of the substrate, and in particular from the substrate surface,between reactant pulses. In some embodiments the reaction chamber ispurged between reactant pulses, such as by purging with an inert gas.The flow rate and time of each reactant, is tunable, as is the removalstep, allowing for control of the quality and various properties of thefilms.

As mentioned above, in some embodiments a gas is provided to thereaction chamber continuously during each deposition cycle, or duringthe entire ALD process, and reactive species are provided by generatinga plasma in the gas, either in the reaction chamber or upstream of thereaction chamber. In some embodiments the gas comprises nitrogen. Insome embodiments the gas is nitrogen. In other embodiments the gas maycomprise helium, or argon. In some embodiments the gas is helium ornitrogen. The flowing gas may also serve as a purge gas for the firstand/or second reactant (or reactive species). For example, flowingnitrogen may serve as a purge gas for a first silicon precursor and alsoserve as a second reactant (as a source of reactive species). In someembodiments, nitrogen, argon, or helium may serve as a purge gas for afirst precursor and a source of excited species for converting thesilicon precursor to the silicon nitride film. In some embodiments thegas in which the plasma is generated does not comprise argon and theadsorbed silicon precursor is not contacted with a reactive speciesgenerated by a plasma from Ar.

The cycle is repeated until a film of the desired thickness andcomposition is obtained. In some embodiments the deposition parameters,such as the flow rate, flow time, purge time, and/or reactantsthemselves, may be varied in one or more deposition cycles during theALD process in order to obtain a film with the desired characteristics.In some embodiments, hydrogen and/or hydrogen plasma are not provided ina deposition cycle, or in the deposition process.

The term “pulse” may be understood to comprise feeding reactant into thereaction chamber for a predetermined amount of time. The term “pulse”does not restrict the length or duration of the pulse and a pulse can beany length of time.

In some embodiments, the silicon reactant is provided first. After aninitial surface termination, if necessary or desired, a first siliconreactant pulse is supplied to the workpiece. In accordance with someembodiments, the first reactant pulse comprises a carrier gas flow and avolatile silicon species, such as H₂SiI₂, that is reactive with theworkpiece surfaces of interest. Accordingly, the silicon reactantadsorbs upon these workpiece surfaces. The first reactant pulseself-saturates the workpiece surfaces such that any excess constituentsof the first reactant pulse do not further react with the molecularlayer formed by this process.

The first silicon reactant pulse is preferably supplied in gaseous form.The silicon precursor gas is considered “volatile” for purposes of thepresent description if the species exhibits sufficient vapor pressureunder the process conditions to transport the species to the workpiecein sufficient concentration to saturate exposed surfaces.

In some embodiments the silicon reactant pulse is from about 0.05seconds to about 5.0 seconds, about 0.1 seconds to about 3 seconds orabout 0.2 seconds to about 1.0 seconds. The optimum pulsing time can bereadily determined by the skilled artisan based on the particularcircumstances.

In some embodiments the silicon reactant consumption rate is selected toprovide a desired dose of precursor to the reaction space. Reactantconsumption refers to the amount of reactant consumed from the reactantsource, such as a reactant source bottle, and can be determined byweighing the reactant source before and after a certain number ofdeposition cycles and dividing the mass difference by the number ofcycles. In some embodiments the silicon reactant consumption is morethan about 0.1 mg/cycle. In some embodiments the silicon reactantconsumption is about 0.1 mg/cycle to about 50 mg/cycle, about 0.5mg/cycle to about 30 mg/cycle or about 2 mg/cycle to about 20 mg/cycle.In some embodiments the minimum preferred silicon reactant consumptionmay be at least partly defined by the reactor dimensions, such as theheated surface area of the reactor. In some embodiments in a showerheadreactor designed for 300 mm silicon wafers, silicon reactant consumptionis more than about 0.5 mg/cycle, or more than about 2.0 mg/cycle. Insome embodiments the silicon reactant consumption is more than about 5mg/cycle in a showerhead reactor designed for 300 mm silicon wafers. Insome embodiments the silicon reactant consumption is more than about 1mg/cycle, preferably more than 5 mg/cycle at reaction temperatures belowabout 400° C. in a showerhead reactor designed for 300 mm siliconwafers.

After sufficient time for a molecular layer to adsorb on the substratesurface, excess first silicon reactant is then removed from the reactionspace. In some embodiments the excess first reactant is purged bystopping the flow of the first chemistry while continuing to flow acarrier gas or purge gas for a sufficient time to diffuse or purgeexcess reactants and reactant by-products, if any, from the reactionspace. In some embodiments the excess first precursor is purged with theaid of inert gas, such as nitrogen or argon, that is flowing throughoutthe ALD cycle.

In some embodiments, the first reactant is purged for about 0.1 secondsto about 10 seconds, about 0.3 seconds to about 5 seconds or about 0.3seconds to about 1 second. Provision and removal of the silicon reactantcan be considered the first or silicon phase of the ALD cycle.

In the second phase, a second reactant comprising a reactive species,such as nitrogen plasma is provided to the workpiece. Nitrogen, N₂, isflowed continuously to the reaction chamber during each ALD cycle insome embodiments. Nitrogen plasma may be formed by generating a plasmain nitrogen in the reaction chamber or upstream of the reaction chamber,for example by flowing the nitrogen through a remote plasma generator.

In some embodiments, plasma is generated in flowing H₂ and N₂ gases. Insome embodiments the H₂ and N₂ are provided to the reaction chamberbefore the plasma is ignited or nitrogen and hydrogen atoms or radicalsare formed. Without being bound to any theory, it is believed that thehydrogen may have a beneficial effect on the ligand removal step i.e. itmay remove some of the remaining ligands or have other beneficialeffects on the film quality. In some embodiments the H₂ and N₂ areprovided to the reaction chamber continuously and nitrogen and hydrogencontaining plasma, atoms or radicals is created or supplied when needed.

Typically, the second reactant, for example comprising nitrogen plasma,is provided for about 0.1 seconds to about 10 seconds. In someembodiments the second reactant, such as nitrogen plasma, is providedfor about 0.1 seconds to about 10 seconds, 0.5 seconds to about 5seconds or 0.5 seconds to about 2.0 seconds. However, depending on thereactor type, substrate type and its surface area, the second reactantpulsing time may be even higher than about 10 seconds. In someembodiments, pulsing times can be on the order of minutes. The optimumpulsing time can be readily determined by the skilled artisan based onthe particular circumstances.

In some embodiments the second reactant is provided in two or moredistinct pulses, without introducing another reactant in between any ofthe two or more pulses. For example, in some embodiments a nitrogenplasma is provided in two or more, preferably in two, sequential pulses,without introducing a Si-precursor in between the sequential pulses. Insome embodiments during provision of nitrogen plasma two or moresequential plasma pulses are generated by providing a plasma dischargefor a first period of time, extinguishing the plasma discharge for asecond period of time, for example from about 0.1 seconds to about 10seconds, from about 0.5 seconds to about 5 seconds or about 1.0 secondsto about 4.0 seconds, and exciting it again for a third period of timebefore introduction of another precursor or a removal step, such asbefore the Si-precursor or a purge step. Additional pulses of plasma canbe introduced in the same way. In some embodiments a plasma is ignitedfor an equivalent period of time in each of the pulses.

Nitrogen plasma may be generated by applying RF power of from about 10 Wto about 2000 W, preferably from about 50 W to about 1000 W, morepreferably from about 100 W to about 500 W in some embodiments. In someembodiments the RF power density may be from about 0.02 W/cm² to about2.0 W/cm², preferably from about 0.05 W/cm² to about 1.5 W/cm². The RFpower may be applied to nitrogen that flows during the nitrogen plasmapulse time, that flows continuously through the reaction chamber, and/orthat flows through a remote plasma generator. Thus in some embodimentsthe plasma is generated in situ, while in other embodiments the plasmais generated remotely. In some embodiments a showerhead reactor isutilized and plasma is generated between a susceptor (on top of whichthe substrate is located) and a showerhead plate. In some embodimentsthe gap between the susceptor and showerhead plate is from about 0.1 cmto about 20 cm, from about 0.5 cm to about 5 cm, or from about 0.8 cm toabout 3.0 cm.

After a time period sufficient to completely saturate and react thepreviously adsorbed molecular layer with the nitrogen plasma pulse, anyexcess reactant and reaction byproducts are removed from the reactionspace. As with the removal of the first \reactant, this step maycomprise stopping the generation of reactive species and continuing toflow the inert gas, such as nitrogen or argon for a time periodsufficient for excess reactive species and volatile reaction by-productsto diffuse out of and be purged from the reaction space. In otherembodiments a separate purge gas may be used. The purge may, in someembodiments, be from about 0.1 seconds to about 10 seconds, about 0.1seconds to about 4 seconds or about 0.1 seconds to about 0.5 seconds.Together, the nitrogen plasma provision and removal represent a second,reactive species phase in a silicon nitride atomic layer depositioncycle.

The two phases together represent one ALD cycle, which is repeated toform silicon nitride thin films of a desired thickness. While the ALDcycle is generally referred to herein as beginning with the siliconphase, it is contemplated that in other embodiments the cycle may beginwith the reactive species phase. One of skill in the art will recognizethat the first precursor phase generally reacts with the terminationleft by the last phase in the previous cycle. Thus, while no reactantmay be previously adsorbed on the substrate surface or present in thereaction space if the reactive species phase is the first phase in thefirst ALD cycle, in subsequent cycles the reactive species phase willeffectively follow the silicon phase. In some embodiments one or moredifferent ALD cycles are provided in the deposition process.

According to some embodiments of the present disclosure, PEALD reactionsmay be performed at temperatures ranging from about 25° C. to about 700°C., preferably from about 50° C. to about 600° C., more preferably fromabout 100° C. to about 450° C., and most preferably from about 200° C.to about 400° C. In some embodiments, the optimum reactor temperaturemay be limited by the maximum allowed thermal budget. Therefore, in someembodiments the reaction temperature is from about 300° C. to about 400°C. In some applications, the maximum temperature is around about 400°C., and, therefore the PEALD process is run at that reactiontemperature.

According to some embodiments of the present disclosure, the pressure ofthe reaction chamber during processing is maintained at from about 0.01torr to about 50 torr, preferably from about 0.1 torr to about 10 torr.

Si Precursors

A number of suitable silicon precursors can be used in the presentlydisclosed PEALD processes. At least some of the suitable precursors mayhave the following general formula:H_(2n+2−y−z)Si_(n)X_(y)A_(z)  (1)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−z), z=0 or more        (and up to 2n+2−y), X is I or Br, and A is a halogen other than        X, preferably n=1-5 and more preferably n=1-3 and most        preferably 1-2.

According to some embodiments, silicon precursors may comprise one ormore cyclic compounds. Such precursors may have the following generalformula:H_(2n−y−z)Si_(n)X_(y)A_(z)  (2)

-   -   wherein the formula (2) compound is cyclic compound, n=3-10, y=1        or more (and up to 2n−z), z=0 or more (and up to 2n−y), X is I        or Br, and A is a halogen other than X, preferably n=3-6.

According to some embodiments, silicon precursors may comprise one ormore iodosilanes. Such precursors may have the following generalformula:H_(2n+2−y−z)Si_(n)I_(y)A_(z)  (3)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−z), z=0 or more        (and up to 2n+2−y), and A is a halogen other than I, preferably        n=1-5 and more preferably n=1-3 and most preferably 1-2.

According to some embodiments, some silicon precursors may comprise oneor more cyclic iodosilanes. Such precursors may have the followinggeneral formula:H_(2n−y−z)Si_(n)I_(y)A_(z)  (4)

-   -   wherein the formula (4) compound is a cyclic compound, n=3-10,        y=1 or more (and up to 2n−z), z=0 or more (and up to 2n−y), and        A is a halogen other than I, preferably n=3-6.

According to some embodiments, some silicon precursors may comprise oneor more bromosilanes. Such precursors may have the following generalformula:H_(2n+2−y−z)Si_(n)Br_(y)A_(z)  (5)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−z), z=0 or more        (and up to 2n+2−y), and A is a halogen other than Br, preferably        n=1-5 and more preferably n=1-3 and most preferably 1-2.

According to some embodiments, some silicon precursors may comprise oneor more cyclic bromosilanes. Such precursors may have the followinggeneral formula:H_(2n−y−z)Si_(n)Br_(y)A_(z)  (6)

-   -   wherein the formula (6) compound is a cyclic compound, n=3-10,        y=1 or more (and up to 2n−z), z=0 or more (and up to 2n−y), and        A is a halogen other than Br, preferably n=3-6.

According to some embodiments, preferred silicon precursors comprise oneor more iodosilanes. Such precursors may have the following generalformula:H_(2n+2−y)Si_(n)I_(y)  (7)

-   -   wherein, n=1-5, y=1 or more (up to 2n+2), preferably n=1-3 and        more preferably n=1-2.

According to some embodiments, preferred silicon precursors comprise oneor more bromosilanes. Such precursors may have the following generalformula:H_(2n+2−y)Si_(n)Br_(y)  (8)

-   -   wherein, n=1-5, y=1 or more (up to 2n+2), preferably n=1-3 and        more preferably n=1-2.

According to some embodiments of a PEALD process, suitable siliconprecursors can include at least compounds having any one of the generalformulas (1) through (8). In general formulas (1) through (8),halides/halogens can include F, Cl, Br and I. In some embodiments, asilicon precursor comprises SiI₄, HSiI₃, H₂SiI₂, H₃SiI, Si₂I₆, HSi₂I₅,H₂Si₂I₄, H₃Si₂I₃, H₄Si₂I₂, H₅Si₂I, or Si₃I₈. In some embodiments, asilicon precursor comprises one of HSiI₃, H₂SiI₂, H₃SiI, H₂Si₂I₄,H₄Si₂I₂, and H₅Si₂I. In some embodiments the silicon precursor comprisestwo, three, four, five or six of HSiI₃, H₂SiI₂, H₃SiI, H₂Si₂I₄, H₄Si₂I₂,and H₅Si₂I, including any combinations thereof.

In certain embodiments, the Si precursor is H₂SiI₂.

In some embodiments, Si precursors of formulas (9)-(28), below, can beused in PEALD processes.

N Precursors

As discussed above, the second reactant according to the presentdisclosure may comprise a nitrogen precursor. In some embodiments thesecond reactant in a PEALD process may comprise a reactive species.Suitable plasma compositions include nitrogen plasma, radicals ofnitrogen, or atomic nitrogen in one form or another. In someembodiments, the reactive species may comprise N-containing plasma or aplasma comprising N. In some embodiments, the reactive species maycomprise a plasma comprising N-containing species. In some embodimentsthe reactive species may comprise nitrogen atoms and/or N* radicals. Insome embodiments, hydrogen plasma, radicals of hydrogen, or atomichydrogen in one form or another are also provided. And in someembodiments, a plasma may also contain noble gases, such as He, Ne, Ar,Kr and Xe, preferably Ar or He, in plasma form, as radicals, or inatomic form. In some embodiments, the second reactant does not compriseany species from a noble gas, such as Ar. Thus, in some embodimentsplasma is not generated in a gas comprising a noble gas.

Thus, in some embodiments the second reactant may comprise plasma formedfrom compounds having both N and H, such as NH₃ and N₂H₄, a mixture ofN₂/H₂ or other precursors having an N—H bond. In some embodiments thesecond reactant may be formed, at least in part, from N₂. In someembodiments the second reactant may be formed, at least in part, from N₂and H₂, where the N₂ and H₂ are provided at a flow ratio (N₂/H₂) fromabout 20:1 to about 1:20, preferably from about 10:1 to about 1:10, morepreferably from about 5:1 to about 1:5 and most preferably from about1:2 to about 4:1, and in some cases 1:1.

The second reactant may be formed in some embodiments remotely viaplasma discharge (“remote plasma”) away from the substrate or reactionspace. In some embodiments, the second reactant may be formed in thevicinity of the substrate or directly above substrate (“direct plasma”).

FIG. 3 is a flow chart generally illustrating a silicon nitride PEALDdeposition cycle that can be used to deposit a silicon nitride thin filmin accordance with some embodiments. According to certain embodiment, asilicon nitride thin film is formed on a substrate by a PEALD-typeprocess comprising multiple silicon nitride deposition cycles, eachsilicon nitride deposition cycle 300 comprising:

(1) contacting a substrate with a vaporized silicon precursor 310 suchthat silicon species adsorb on the substrate surface;

(2) introduction of a nitrogen precursor into a reaction space 320;

(3) generating a reactive species from a nitrogen precursor 330; and

(4) contacting the substrate with the reactive species 340, therebyconverting the adsorbed silicon compound into silicon nitride.

Nitrogen may flow continuously throughout the cycle, with nitrogenplasma formed at the appropriate times to convert adsorbed siliconcompound into silicon nitride.

As mentioned above, in some embodiments the substrate may be contactedsimultaneously with the silicon compound and the reactive species, whilein other embodiments these reactants are provided separately.

The contacting steps are repeated 350 until a thin film of a desiredthickness and composition is obtained. Excess reactants may be purgedfrom the reaction space after each contacting step, i.e., steps 310 and340.

According to some embodiments, a silicon nitride thin film is depositedusing a PEALD process on a substrate having three-dimensional features,such as in a FinFET application. The process may comprise the followingsteps:

(1) a substrate comprising a three-dimensional structure is provided ina reaction space;

(2) a silicon-containing precursor, such as SiI₂H₂, is introduced intothe reaction space so that silicon-containing species are adsorbed to asurface of the substrate;

(3) excess silicon-containing precursor and reaction byproducts areremoved from the reaction space;

(4) a nitrogen-containing precursor, such as N₂, NH₃, N₂H₄, or N₂ andH₂, is introduced into the reaction space;

(5) generating reactive species from the nitrogen precursor;

(6) contacting the substrate with the reactive species; and

(7) removing excess nitrogen atoms, plasma, or radicals and reactionbyproducts;

Steps (2) through (7) may be repeated until a silicon nitride film of adesired thickness is formed.

In some embodiments steps (5) and (6) are replaced by a step in whichthe nitrogen atoms, plasma or radicals are formed remotely and providedto the reaction space.

In some embodiments, the PEALD process is performed at a temperaturebetween about 200° C. to about 400° C., between about 300° C. and about400° C., or at about 400° C.

Thermal ALD Processes

The methods presented herein also allow deposition of silicon nitridefilms on substrate surfaces by thermal ALD processes. Geometricallychallenging applications, such as 3-dimensional structures, are alsopossible with these thermal processes. According to some embodiments,thermal atomic layer deposition (ALD) type processes are used to formsilicon nitride films on substrates such as integrated circuitworkpieces.

A substrate or workpiece is placed in a reaction chamber and subjectedto alternately repeated, self-limiting surface reactions. Preferably,for forming silicon nitride films each thermal ALD cycle comprises atleast two distinct phases. The provision and removal of a reactant fromthe reaction space may be considered a phase. In a first phase, a firstreactant comprising silicon is provided and forms no more than about onemonolayer on the substrate surface. This reactant is also referred toherein as “the silicon precursor” or “silicon reactant” and may be, forexample, H₂SiI₂. In a second phase, a second reactant comprising anitrogen-containing compound is provided and reacts with the adsorbedsilicon precursor to form SiN. This second reactant may also be referredto as a “nitrogen precursor” or “nitrogen reactant.” The second reactantmay comprise NH₃ or another suitable nitrogen-containing compound.Additional phases may be added and phases may be removed as desired toadjust the composition of the final film.

One or more of the reactants may be provided with the aid of a carriergas, such as Ar or He. In some embodiments the silicon precursor and thenitrogen precursor are provided with the aid of a carrier gas.

In some embodiments, two of the phases may overlap, or be combined. Forexample, the silicon precursor and the nitrogen precursor may beprovided simultaneously in pulses that partially or completely overlap.In addition, although referred to as the first and second phases, andthe first and second reactants, the order of the phases and the order ofprovision of reactants may be varied, and an ALD cycle may begin withany one of the phases or any of the reactants. That is, unless specifiedotherwise, the reactants can be provided in any order and the processmay begin with any of the reactants.

As discussed in more detail below, in some embodiments for depositing asilicon nitride film, one or more deposition cycles typically beginswith provision of the silicon precursor followed by the nitrogenprecursor. In some embodiments, one or more deposition cycles beginswith provision of the nitrogen precursor followed by the siliconprecursor.

Again, one or more of the reactants may be provided with the aid of acarrier gas, such as Ar or He. In some embodiments the nitrogenprecursor is provided with the aid of a carrier gas. In someembodiments, although referred to as a first phase and a second phaseand a first and second reactant, the order of the phases and thus theorder of provision of the reactants may be varied, and an ALD cycle maybegin with any one of the phases.

In some embodiments the substrate on which deposition is desired, suchas a semiconductor workpiece, is loaded into a reactor. The reactor maybe part of a cluster tool in which a variety of different processes inthe formation of an integrated circuit are carried out. In someembodiments a flow-type reactor is utilized. In some embodiments ashower head type of reactor is utilized. In some embodiments a spacedivided reactor is utilized. In some embodiments a high-volumemanufacturing-capable single wafer ALD reactor is used. In otherembodiments a batch reactor comprising multiple substrates is used. Forembodiments in which batch ALD reactors are used, the number ofsubstrates is preferably in the range of 10 to 200, more preferably inthe range of 50 to 150, and most preferably in the range of 100 to 130.

Exemplary single wafer reactors, designed specifically to enhance ALDprocesses, are commercially available from ASM America, Inc. (Phoenix,Ariz.) under the tradenames Pulsar® 2000 and Pulsar® 3000 and ASM JapanK.K (Tokyo, Japan) under the tradename Eagle® XP, XP8 and Dragon®.Exemplary batch ALD reactors, designed specifically to enhance ALDprocesses, are commercially available from and ASM Europe B.V (Almere,Netherlands) under the tradenames A400™ and A412™.

In some embodiments, if necessary, the exposed surfaces of the workpiececan be pretreated to provide reactive sites to react with the firstphase of the ALD process. In some embodiments a separate pretreatmentstep is not required. In some embodiments the substrate is pretreated toprovide a desired surface termination.

In some embodiments, excess reactant and reaction byproducts, if any,are removed from the vicinity of the precursor, such as from thesubstrate surface, between reactant pulses. In some embodiments excessreactant and reaction byproducts are removed from the reaction chamberby purging between reactant pulses, for example with an inert gas. Theflow rate and time of each reactant, is tunable, as is the purge step,allowing for control of the quality and properties of the films. In someembodiments removing excess reactant and/or reaction byproductscomprises moving the substrate.

As mentioned above, in some embodiments, a gas is provided to thereaction chamber continuously during each deposition cycle, or duringthe entire ALD process. In other embodiments the gas may be nitrogen,helium or argon.

The ALD cycle is repeated until a film of the desired thickness andcomposition is obtained. In some embodiments the deposition parameters,such as the flow rate, flow time, purge time, and/or precursorsthemselves, may be varied in one or more deposition cycles during theALD process in order to obtain a film with the desired characteristics.

The term “pulse” may be understood to comprise feeding reactant into thereaction chamber for a predetermined amount of time. The term “pulse”does not restrict the length or duration of the pulse and a pulse can beany length of time.

In some embodiments, the silicon precursor is provided first. After aninitial surface termination, if necessary or desired, a first siliconprecursor pulse is supplied to the workpiece. In accordance with someembodiments, the first precursor pulse comprises a carrier gas flow anda volatile silicon species, such as H₂SiI₂, that is reactive with theworkpiece surfaces of interest. Accordingly, the silicon precursoradsorbs upon the workpiece surfaces. The first precursor pulseself-saturates the workpiece surfaces such that any excess constituentsof the first precursor pulse do not substantially react further with themolecular layer formed by this process.

The first silicon precursor pulse is preferably supplied in gaseousform. The silicon precursor gas is considered “volatile” for purposes ofthe present description if the species exhibits sufficient vaporpressure under the process conditions to transport the species to theworkpiece in sufficient concentration to saturate exposed surfaces.

In some embodiments the silicon precursor pulse is from about 0.05seconds to about 5.0 seconds, about 0.1 seconds to about 3 seconds orabout 0.2 seconds to about 1.0 second. In batch process the siliconprecursor pulses can be substantially longer as can be determined by theskilled artisan given the particular circumstances.

After sufficient time for a molecular layer to adsorb on the substratesurface, excess first precursor is then removed from the reaction space.In some embodiments the excess first precursor is purged by stopping theflow of the first precursor while continuing to flow a carrier gas orpurge gas for a sufficient time to diffuse or purge excess reactants andreactant by-products, if any, from the reaction space.

In some embodiments, the first precursor is purged for about 0.1 secondsto about 10 seconds, about 0.3 seconds to about 5 seconds or about 0.3seconds to about 1 seconds. Provision and removal of the siliconprecursor can be considered the first or silicon phase of the ALD cycle.In batch process the first precursor purge can be substantially longeras can be determined by the skilled artisan given the specificcircumstances.

A second, nitrogen precursor is pulsed into the reaction space tocontact the substrate surface. The nitrogen precursor may be providedwith the aid of a carrier gas. The nitrogen precursor may be, forexample, NH₃ or N₂H₄. The nitrogen precursor pulse is also preferablysupplied in gaseous form. The nitrogen precursor is considered“volatile” for purposes of the present description if the speciesexhibits sufficient vapor pressure under the process conditions totransport the species to the workpiece in sufficient concentration tosaturate exposed surfaces.

In some embodiments, the nitrogen precursor pulse is about 0.05 secondsto about 5.0 seconds, 0.1 seconds to about 3.0 seconds or about 0.2seconds to about 1.0 second. In batch process the nitrogen precursorpulses can be substantially longer as can be determined by the skilledartisan given the specific circumstances.

After sufficient time for a molecular layer to adsorb on the substratesurface at the available binding sites, the second, nitrogen precursoris then removed from the reaction space. In some embodiments the flow ofthe second nitrogen precursor is stopped while continuing to flow acarrier gas for a sufficient time to diffuse or purge excess reactantsand reactant by-products, if any, from the reaction space, preferablywith greater than about two reaction chamber volumes of the purge gas,more preferably with greater than about three chamber volumes. Provisionand removal of the nitrogen precursor can be considered the second ornitrogen phase of the ALD cycle.

In some embodiments, the nitrogen precursor is purged for about 0.1seconds to about 10.0 seconds, about 0.3 seconds to about 5.0 seconds orabout 0.3 seconds to about 1.0 second. In batch process the firstprecursor purge can be substantially longer as can be determined by theskilled artisan given the specific circumstances.

The flow rate and time of the nitrogen precursor pulse, as well as theremoval or purge step of the nitrogen phase, are tunable to achieve adesired composition in the silicon nitride film. Although the adsorptionof the nitrogen precursor on the substrate surface is typicallyself-limiting, due to the limited number of binding sites, pulsingparameters can be adjusted such that less than a monolayer of nitrogenis adsorbed in one or more cycles.

The two phases together represent one ALD cycle, which is repeated toform silicon nitrogen thin films of the desired thickness. While the ALDcycle is generally referred to herein as beginning with the siliconphase, it is contemplated that in other embodiments the cycle may beginwith the nitrogen phase. One of skill in the art will recognize that thefirst precursor phase generally reacts with the termination left by thelast phase in the previous cycle. In some embodiments one or moredifferent ALD cycles are provided in the deposition process.

According to some embodiments of the present disclosure, ALD reactionsmay be performed at temperatures ranging from about 25° C. to about1000° C., preferably from about 100° C. to about 800° C., morepreferably from about 200° C. to about 650° C., and most preferably fromabout 300° C. to about 500° C. In some embodiments, the optimum reactortemperature may be limited by the maximum allowed thermal budget.Therefore, the reaction temperature can be from about 300° C. to about400° C. In some applications, the maximum temperature is around about400° C., and, therefore, the process is run at that reactiontemperature.

Si Precursors

A number of suitable silicon precursors may be used in the presentlydisclosed thermal processes, such as thermal ALD processes. In someembodiments these precursors may also be used in plasma ALD processes inwhich a film with a desired quality (at least one of the desired WER,WERR, pattern loading effect or/and step coverage features describedbelow) is deposited.

According to some embodiments, some silicon precursors comprise iodineand the film deposited by using that precursor has at least one desiredproperty, for example at least one of the desired WER, WERR, patternloading effect or/and step coverage features described below.

According to some embodiments, some silicon precursors comprise bromineand the film deposited by using that precursor have at least one desiredproperty, for example at least one of the desired WER, WERR, patternloading effect or/and step coverage features described below.

At least some of the suitable precursors may have the following generalformula:H_(2n+2−y−z−w)Si_(n)X_(y)A_(z)R_(w)  (9)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−z−w), z=0 or more        (and up to 2n+2−y−w), w=0 or more (and up to 2n+2−y−z), X is I        or Br, A is a halogen other than X, R is an organic ligand and        can be independently selected from the group consisting of        alkoxides, alkylsilyls, alkyl, substituted alkyl, alkylamines        and unsaturated hydrocarbon; preferably n=1-5 and more        preferably n=1-3 and most preferably 1-2. Preferably R is a        C₁-C₃ alkyl ligand, such as methyl, ethyl, n-propyl or        isopropyl.

According to some embodiments, some silicon precursors comprise one ormore cyclic compounds. Such precursors may have the following generalformula:H_(2n−y−z−w)Si_(n)X_(y)A_(z)R_(w)  (10)

-   -   wherein, n=3-10, y=1 or more (and up to 2n−z−w), z=0 or more        (and up to 2n−y−w), w=0 or more (and up to 2n−y−z), X is I or        Br, A is a halogen other than X, R is an organic ligand and can        be independently selected from the group consisting of        alkoxides, alkylsilyls, alkyl, substituted alkyl, alkylamines        and unsaturated hydrocarbon; preferably n=3-6. Preferably R is a        C₁-C₃ alkyl ligand, such as methyl, ethyl, n-propyl or        isopropyl.

According to some embodiments, some silicon precursors comprise one ormore iodosilanes. Such precursors may have the following generalformula:H_(2n+2−y−z−w)Si_(n)I_(y)A_(z)R_(w)  (11)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−z−w), z=0 or more        (and up to 2n+2−y−w), w=0 or more (and up to 2n+2−y−z), A is a        halogen other than I, R is an organic ligand and can be        independently selected from the group consisting of alkoxides,        alkylsilyls, alkyl, substituted alkyl, alkylamines and        unsaturated hydrocarbon; preferably n=1-5 and more preferably        n=1-3 and most preferably 1-2. Preferably R is a C₁-C₃ alkyl        ligand, such as methyl, ethyl, n-propyl or isopropyl.

According to some embodiments, some silicon precursors comprise one ormore cyclic iodosilanes. Such precursors may have the following generalformula:H_(2n−y−z−w)Si_(n)I_(y)A_(z)R_(w)  (12)

-   -   wherein, n=3-10, y=1 or more (and up to 2n−z−w), z=0 or more        (and up to 2n−y−w), w=0 or more (and up to 2n−y−z), A is a        halogen other than I, R is an organic ligand and can be        independently selected from the group consisting of alkoxides,        alkylsilyls, alkyl, substituted alkyl, alkylamines and        unsaturated hydrocarbon; preferably n=3-6. Preferably R is a        C₁-C₃ alkyl ligand, such as methyl, ethyl, n-propyl or        isopropyl.

According to some embodiments, some silicon precursors comprise one ormore bromosilanes. Such precursors may have the following generalformula:H_(2n+2−y−z−w)Si_(n)Br_(y)A_(z)R_(w)  (13)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−z−w), z=0 or more        (and up to 2n+2−y−w), w=0 or more (and up to 2n+2−y−z), A is a        halogen other than Br, R is an organic ligand and can be        independently selected from the group consisting of alkoxides,        alkylsilyls, alkyl, substituted alkyl, alkylamines and        unsaturated hydrocarbon; preferably n=1-5 and more preferably        n=1-3 and most preferably 1-2. Preferably R is a C₁-C₃ alkyl        ligand, such as methyl, ethyl, n-propyl or isopropyl.

According to some embodiments, some silicon precursors comprise one ormore cyclic bromosilanes. Such precursors may have the following generalformula:H_(2n−y−z−w)Si_(n)Br_(y)A_(z)R_(w)  (14)

-   -   wherein, n=3-10, y=1 or more (and up to 2n−z−w), z=0 or more        (and up to 2n−y−w), w=0 or more (and up to 2n−y−z), A is a        halogen other than Br, R is an organic ligand and can be        independently selected from the group consisting of alkoxides,        alkylsilyls, alkyl, substituted alkyl, alkylamines and        unsaturated hydrocarbon; preferably n=3-6. Preferably R is a        C₁-C₃ alkyl ligand such as methyl, ethyl, n-propyl or isopropyl.

According to some embodiments, some silicon precursors comprise one ormore iodosilanes or bromosilanes in which the iodine or bromine is notbonded to the silicon in the compound. Accordingly some suitablecompounds may have iodine/bromine substituted alkyl groups. Suchprecursors may have the following general formula:H_(2n+2−y−z−w)Si_(n)X_(y)A_(z)R^(II) _(w)  (15)

-   -   wherein, n=1-10, y=0 or more (and up to 2n+2−z−w), z=0 or more        (and up to 2n+2−y−w), w=1 or more (and up to 2n+2−y−z), X is I        or Br, A is a halogen other than X, R^(II) is an organic ligand        containing I or Br and can be independently selected from the        group consisting of I or Br substituted alkoxides, alkylsilyls,        alkyls, alkylamines and unsaturated hydrocarbons; preferably        n=1-5 and more preferably n=1-3 and most preferably 1-2.        Preferably R^(II) is an iodine substituted C₁-C₃ alkyl ligand.

According to some embodiments, some silicon precursors comprise one ormore cyclic iodosilanes or bromosilanes. Accordingly some suitablecyclic compounds may have iodine/bromine substituted alkyl groups. Suchprecursors may have the following general formula:H_(2n−y−z−w)Si_(n)X_(y)A_(z)R^(II) _(w)  (16)

-   -   wherein, n=3-10, y=0 or more (and up to 2n+2−z−w), z=0 or more        (and up to 2n+2−y−w), w=1 or more (and up to 2n+2−y−z), X is I        or Br, A is a halogen other than X, R^(II) is an organic ligand        containing I or Br and can be independently selected from the        group consisting of I or Br substituted alkoxides, alkylsilyls,        alkyls, alkylamines and unsaturated hydrocarbons; preferably        n=3-6. Preferably R is an iodine substituted C₁-C₃ alkyl ligand.

According to some embodiments, some suitable silicon precursors may haveat least one of the following general formulas:H_(2n+2−y−z−w)Si_(n)X_(y)A_(z)(NR₁R₂)_(w)  (17)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−z−w), z=0 or more        (and up to 2n+2−y−w), w=1 or more (and up to 2n+2−y−z), X is I        or Br, A is a halogen other than X, N is nitrogen and R₁ and R₂        can be independently selected from the group consisting of        hydrogen, alkyl, substituted alkyl, silyl, alkylsilyl and        unsaturated hydrocarbon; preferably n=1-5 and more preferably        n=1-3 and most preferably 1-2. Preferably R₁ and R₂ are hydrogen        or C₁-C₄ alkyl groups, such as methyl, ethyl, n-propyl,        isopropyl, t-butyl, isobutyl, sec-butyl and n-butyl. More        preferably R₁ and R₂ are hydrogen or C₁-C₃ alkyl groups, such as        methyl, ethyl, n-propyl or isopropyl. Each of the (NR₁R₂)_(w)        ligands can be independently selected from each other.        (H_(3−y−z−w)X_(y)A_(z)(NR₁R₂)_(w)Si)₃—N  (18)    -   wherein, y=1 or more (and up to 3−z−w), z=0 or more (and up to        3−y−w), w=1 or more (and up to 3−y−z), X is I or Br, A is a        halogen other than X, N is nitrogen and R₁ and R₂ can be        independently selected from the group consisting of hydrogen,        alkyl, substituted alkyl, silyl, alkylsilyl, and unsaturated        hydrocarbon. Preferably R₁ and R₂ are hydrogen or C₁-C₄ alkyl        groups, such as methyl, ethyl, n-propyl, isopropyl, t-butyl,        isobutyl, sec-butyl and n-butyl. More preferably R₁ and R₂ are        hydrogen or C₁-C₃ alkyl groups, such as methyl, ethyl, n-propyl        or isopropyl. Each of the (NR₁R₂)_(w) ligands can be        independently selected from each other. Each of the three        H_(3−y−z−w)X_(y)A_(z)(NR₁R₂)_(w)Si ligands can be independently        selected from each other.

In some embodiments, some suitable precursors may have at least one ofthe following more specific formulas:H_(2n+2−y−w)Si_(n)I_(y)(NR₁R₂)_(w)  (19)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−w), w=1 or more        (and up to 2n+2−y), N is nitrogen, and R₁ and R₂ can be        independently selected from the group consisting of hydrogen,        alkyl, substituted alkyl, silyl, alkylsilyl, and unsaturated        hydrocarbon; preferably n=1-5 and more preferably n=1-3 and most        preferably 1-2. Preferably R₁ and R₂ are hydrogen or C₁-C₄ alkyl        groups, such as methyl, ethyl, n-propyl, isopropyl, t-butyl,        isobutyl, sec-butyl and n-butyl. More preferably R₁ and R₂ are        hydrogen or C₁-C₃ alkyl groups, such as methyl, ethyl, n-propyl        or isopropyl. Each of the (NR₁R₂)_(w) ligands can be        independently selected from each other.        (H_(3−y−w)I_(y)(NR₁R₂)_(w)Si)₃—N  (20)    -   wherein, y=1 or more (and up to 3−w), w=1 or more (and up to        3−y), N is nitrogen and R₁ and R₂ can be independently selected        from the group consisting of hydrogen, alkyl, substituted alkyl,        silyl, alkylsilyl, and unsaturated hydrocarbon. Preferably R₁        and R₂ are hydrogen or C₁-C₄ alkyl groups, such as methyl,        ethyl, n-propyl, isopropyl, t-butyl, isobutyl, sec-butyl and        n-butyl. More preferably R₁ and R₂ are hydrogen or C₁-C₃ alkyl        groups, such as methyl, ethyl, n-propyl or isopropyl. Each of        the three H_(3−y−w)I_(y)(NR₁R₂)_(w)Si ligands can be        independently selected from each other.

According to some embodiments, some suitable silicon precursors may haveat least one of the following general formulas:H_(2n+2−y−z−w)Si_(n)X_(y)A_(z)(NR₁R₂)_(w)  (21)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−z−w), z=0 or more        (and up to 2n+2−y−w), w=1 or more (and up to 2n+2−y−z), X is I        or Br, A is a halogen other than X, N is nitrogen, R₁ can be        independently selected from the group consisting of hydrogen,        alkyl, substituted alkyl, silyl, alkylsilyl, and unsaturated        hydrocarbon, and R₂ can be independently selected from the group        consisting of alkyl, substituted alkyl, silyl, alkylsilyl and        unsaturated hydrocarbon; preferably n=1-5 and more preferably        n=1-3 and most preferably 1-2. Preferably R₁ is hydrogen or        C₁-C₄ alkyl groups, such as methyl, ethyl, n-propyl, isopropyl,        t-butyl, isobutyl, sec-butyl, and n-butyl. More preferably R₁ is        hydrogen or C₁-C₃ alkyl groups, such as methyl, ethyl, n-propyl,        or isopropyl. Preferably R₂ is C₁-C₄ alkyl groups, such as        methyl, ethyl, n-propyl, isopropyl, t-butyl, isobutyl,        sec-butyl, and n-butyl. More preferably R₂ is C₁-C₃ alkyl        groups, such as methyl, ethyl, n-propyl, or isopropyl. Each of        the (NR₁R₂)_(w) ligands can be independently selected from each        other.        (H_(3−y−z−w)X_(y)A_(z)(NR₁R₂)_(w)Si)₃—N  (22)    -   wherein, y=1 or more (and up to 3−z−w), z=0 or more (and up to        3−y−w), w=1 or more (and up to 3−y−z), X is I or Br, A is a        halogen other than X, N is nitrogen, R₁ can be independently        selected from the group consisting of hydrogen, alkyl,        substituted alkyl, silyl, alkylsilyl, and unsaturated        hydrocarbon, and R₂ can be independently selected from the group        consisting of alkyl, substituted alkyl, silyl, alkylsilyl, and        unsaturated hydrocarbon; preferably n=1-5 and more preferably        n=1-3 and most preferably 1-2. Preferably R₁ is hydrogen or        C₁-C₄ alkyl groups, such as methyl, ethyl, n-propyl, isopropyl,        t-butyl, isobutyl, sec-butyl, and n-butyl. More preferably R₁ is        hydrogen or C₁-C₃ alkyl groups, such as methyl, ethyl, n-propyl,        or isopropyl. Preferably R₂ is C₁-C₄ alkyl groups, such as        methyl, ethyl, n-propyl, isopropyl, t-butyl, isobutyl,        sec-butyl, and n-butyl. More preferably R₂ is C₁-C₃ alkyl        groups, such as methyl, ethyl, n-propyl, or isopropyl. Each of        the (NR₁R₂)_(w) ligands can be independently selected from each        other.

In some embodiments, some suitable precursors may have at least one ofthe following more specific formulas:H_(2n+2−y−w)Si_(n)I_(y)(NR₁R₂)_(w)  (23)

-   -   wherein, n=1-10, y=1 or more (and up to 2n+2−w), w=1 or more        (and up to 2n+2−y), N is nitrogen, R₁ can be independently        selected from the group consisting of hydrogen, alkyl,        substituted alkyl, silyl, alkylsilyl, and unsaturated        hydrocarbon, and R₂ can be independently selected from the group        consisting of alkyl, substituted alkyl, silyl, alkylsilyl, and        unsaturated hydrocarbon; preferably n=1-5 and more preferably        n=1-3 and most preferably 1-2. Preferably R₁ is hydrogen or        C₁-C₄ alkyl groups, such as methyl, ethyl, n-propyl, isopropyl,        t-butyl, isobutyl, sec-butyl, and n-butyl. More preferably R₁ is        hydrogen or C₁-C₃ alkyl groups, such as methyl, ethyl, n-propyl,        or isopropyl. Preferably R₂ is C₁-C₄ alkyl groups, such as        methyl, ethyl, n-propyl, isopropyl, t-butyl, isobutyl,        sec-butyl, and n-butyl. More preferably R₂ is C₁-C₃ alkyl        groups, such as methyl, ethyl, n-propyl, or isopropyl. Each of        the (NR₁R₂)_(w) ligands can be independently selected from each        other.        (H_(3−y−w)I_(y)(NR₁R₂)_(w)Si)₃—N  (24)    -   wherein, y=1 or more (and up to 3−w), w=1 or more (and up to        3−y), N is nitrogen, R₁ can be independently selected from the        group consisting of hydrogen, alkyl, substituted alkyl, silyl,        alkylsilyl, and unsaturated hydrocarbon, and R₂ can be        independently selected from the group consisting of alkyl,        substituted alkyl, silyl, alkylsilyl, and unsaturated        hydrocarbon; preferably n=1-5 and more preferably n=1-3 and most        preferably 1-2. Preferably R₁ is hydrogen or C₁-C₄ alkyl groups,        such as methyl, ethyl, n-propyl, isopropyl, t-butyl, isobutyl,        sec-butyl, and n-butyl. More preferably R₁ is hydrogen or C₁-C₃        alkyl groups, such as methyl, ethyl, n-propyl, or isopropyl.        Preferably R₂ is C₁-C₄ alkyl groups, such as methyl, ethyl,        n-propyl, isopropyl, t-butyl, isobutyl, sec-butyl, and n-butyl.        More preferably R₂ is C₁-C₃ alkyl groups, such as methyl, ethyl,        n-propyl, or isopropyl. Each of the (NR₁R₂)_(w) ligands can be        independently selected from each other.

According to some embodiments of a thermal ALD process, suitable siliconprecursors can include at least compounds having any one of the generalformulas (9) through (24). In general formulas (9) through (18) as wellas in general formulas (21) and (22), halides/halogens can include F,Cl, Br and I.

In some embodiments, a silicon precursor comprises one or more of thefollowing: SiI₄, HSiI₃, H₂SiI₂, H₃SiI, Si₂I₆, HSi₂I₅, H₂Si₂I₄, H₃Si₂I₃,H₄Si₂I₂, H₅Si₂I, Si₃I₈, HSi₂I₅, H₂Si₂I₄, H₃Si₂I₃, H₄Si₂I₂, H₅Si₂I,MeSiI₃, Me₂SiI₂, Me₃SiI, MeSi₂I₅, Me₂Si₂I₄, Me₃Si₂I₃, Me₄Si₂I₂, Me₅Si₂I,HMeSiI₂, HMe₂SiI, HMeSi₂I₄, HMe₂Si₂I₃, HMe₃Si₂I₂, HMe₄Si₂I, H₂MeSiI,H₂MeSi₂I₃, H₂Me₂Si₂I₂, H₂Me₃Si₂I, H₃MeSi₂I₂, H₃Me₂Si₂I, H₄MeSi₂I,EtSiI₃, Et₂SiI₂, Et₃SiI, EtSi₂I₅, Et₂Si₂I₄, Et₃Si₂I₃, Et₄Si₂I₂, Et₅Si₂I,HEtSiI₂, HEt₂SiI, HEtSi₂I₄, HEt₂Si₂I₃, HEt₃Si₂I₂, HEt₄Si₂I, H₂EtSiI,H₂EtSi₂I₃, H₂Et₂Si₂I₂, H₂Et₃Si₂I, H₃EtSi₂I₂, H₃Et₂Si₂I, and H₄EtSi₂I.

In some embodiments, a silicon precursor comprises one or more of thefollowing: EtMeSiI₂, Et₂MeSiI, EtMe₂SiI, EtMeSi₂I₄, Et₂MeSi₂I₃,EtMe₂Si₂I₃, Et₃MeSi₂I₂, Et₂Me₂Si₂I₂, EtMe₃Si₂I₂, Et₄MeSi₂I, Et₃Me₂Si₂I,Et₂Me₃Si₂I, EtMe₄Si₂I, HEtMeSiI, HEtMeSi₂I₃, HEt₂MeSi₂I₂, HEtMe₂Si₂I₂,HEt₃MeSi₂I, HEt₂Me₂Si₂I, HEtMe₃Si₂I, H₂EtMeSi₂I₂, H₂Et₂MeSi₂I,H₂EtMe₂Si₂I, H₃EtMeSi₂I.

In some embodiments, a silicon precursor comprises one or more of thefollowing: HSiI₃, H₂SiI₂, H₃SiI, H₂Si₂I₄, H₄Si₂I₂, H₅Si₂I, MeSiI₃,Me₂SiI₂, Me₃SiI, Me₂Si₂I₄, Me₄Si₂I₂, HMeSiI₂, H₂Me₂Si₂I₂, EtSiI₃,Et₂SiI₂, Et₃SiI, Et₂Si₂I₄, Et₄Si₂I₂, and HEtSiI₂. In some embodiments asilicon precursor comprises two, three, four, five, six, seven, eight,nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen,seventeen, eighteen, nineteen or more compounds selected from HSiI₃,H₂SiI₂, H₃SiI, H₂Si₂I₄, H₄Si₂I₂, H₅Si₂I, MeSiI₃, Me₂SiI₂, Me₃SiI,Me₂Si₂I₄, Me₄Si₂I₂, HMeSiI₂, H₂Me₂Si₂I₂, EtSiI₃, Et₂SiI₂, Et₃SiI,Et₂Si₂I₄, Et₄Si₂I₂, and HEtSiI₂, including any combinations thereof. Incertain embodiments, the silicon precursor is H₂SiI₂.

In some embodiments, a silicon precursor comprises a three iodines andone amine or alkylamine ligands bonded to silicon. In some embodimentssilicon precursor comprises one or more of the following: (SiI₃)NH₂,(SiI₃)NHMe, (SiI₃)NHEt, (SiI₃)NH^(i)Pr, (SiI₃)NH^(t)Bu, (SiI₃)NMe₂,(SiI₃)NMeEt, (SiI₃)NMe^(i)Pr, (SiI₃)NMe^(t)Bu, (SiI₃)NEt₂,(SiI₃)NEt^(i)Pr, (SiI₃)NEt^(t)Bu, (SiI₃)N^(i)Pr₂, (SiI₃)N^(i)Pr^(t)Bu,and (SiI₃)N^(t)Bu₂ In some embodiments, a silicon precursor comprisestwo, three, four, five, six, seven, eight, nine, ten, eleven, twelve,thirteen, fourteen, fifteen or more compounds selected from (SiI₃)NH₂,(SiI₃)NHMe, (SiI₃)NHEt, (SiI₃)NH^(i)Pr, (SiI₃)NH^(t)Bu, (SiI₃)NMe₂,(SiI₃)NMeEt, (SiI₃)NMe^(i)Pr, (SiI₃)NMe^(t)Bu, (SiI₃)NEt₂,(SiI₃)NEt^(i)Pr, (SiI₃)NEt^(t)Bu, (SiI₃)N^(i)Pr₂, (SiI₃)N^(i)Pr^(t)Bu,(SiI₃)N^(t)Bu₂, and combinations thereof. In some embodiments, a siliconprecursor comprises two iodines and two amine or alkylamine ligandsbonded to silicon. In some embodiments, silicon precursor comprises oneor more of the following: (SiI₂)(NH₂)₂, (SiI₂)(NHMe)₂, (SiI₂)(NHEt)₂,(SiI₂)(NH^(i)Pr)₂, (SiI₂)(NH^(t)Bu)₂, (SiI₂)(NMe₂)₂, (SiI₂)(NMeEt)₂,(SiI₂)(NMe^(i)Pr)₂, (SiI2)(NMe^(t)Bu)₂, (SiI₂)(NEt₂)₂,(SiI₂)(NEt^(i)Pr)₂, (SiI₂)(NEt^(t)Bu)₂, (SiI₂)(N^(i)Pr₂)₂,(SiI₂)(N^(i)Pr^(t)Bu)₂, and (SiI₂)(N^(t)Bu)₂. In some embodiments, asilicon precursor comprises two, three, four, five, six, seven, eight,nine, ten, eleven, twelve, thirteen, fourteen, fifteen or more compoundsselected from (SiI₂)(NH₂)₂, (SiI₂)(NHMe)₂, (SiI₂)(NHEt)₂,(SiI₂)(NH^(i)Pr)₂, (SiI₂)(NH^(t)Bu)₂, (SiI₂)(NMe₂)₂, (SiI₂)(NMeEt)₂,(SiI₂)(NMe^(i)Pr)₂, (SiI2)(NMe^(t)Bu)₂, (SiI₂)(NEt₂)₂,(SiI₂)(NEt^(i)Pr)₂, (SiI₂)(NEt^(t)Bu)², (SiI₂)(N^(i)Pr₂)₂,(SiI₂)(N^(i)Pr^(t)Bu)₂, (SiI₂)(N^(t)Bu)₂, and combinations thereof.

In some embodiments, a silicon precursor comprises two iodines, onehydrogen and one amine or alkylamine ligand bonded to silicon. In someembodiments silicon precursor comprises one or more of the following:(SiI₂H)NH₂, (SiI₂H)NHMe, (SiI₂H)NHEt, (SiI₂H)NH^(i)Pr, (SiI₂H)NH^(t)Bu,(SiI₂H)NMe₂, (SiI₂H)NMeEt, (SiI₂H)NMe^(i)Pr, (SiI₂H)NMe^(t)Bu,(SiI₂H)NEt₂, (SiI₂H)NEt^(i)Pr, (SiI₂H)NEt^(t)Bu, (SiI₂H)N^(i)Pr₂,(SiI₂H)N^(i)Pr^(t)Bu, and (SiI₂H)N^(t)Bu₂. In some embodiments a siliconprecursor comprises two, three, four, five, six, seven, eight, nine,ten, eleven, twelve, thirteen, fourteen, fifteen or more compoundsselected from (SiI₂H)NH₂, (SiI₂H)NHMe, (SiI₂H)NHEt, (SiI₂H)NH^(i)Pr,(SiI₂H)NH^(t)Bu, (SiI₂H)NMe₂, (SiI₂H)NMeEt, (SiI₂H)NMe^(i)Pr,(SiI₂H)NMe^(t)Bu, (SiI₂H)NEt₂, (SiI₂H)NEt^(i)Pr, (SiI₂H)NEt^(t)Bu,(SiI₂H)N^(i)Pr₂, (SiI₂H)N^(i)Pr^(t)Bu, (SiI₂H)N^(t)Bu₂, and combinationsthereof.

In some embodiments, a silicon precursor comprises one iodine, onehydrogen and two amine or alkylamine ligand bonded to silicon. In someembodiments, silicon precursor comprises one or more of the following:(SiIH)(NH₂)₂, (SiIH)(NHMe)₂, (SiIH)(NHEt)₂, (SiIH)(NH^(i)Pr)₂,(SiIH)(NH^(t)Bu)₂, (SiIH)(NMe₂)₂, (SiIH)(NMeEt)₂, (SiIH)(NMe^(i)Pr)₂,(SiIH)(NMe^(t)Bu)₂, (SiIH)(NEt₂)₂, (SiIH)(NEt^(i)Pr)₂,(SiIH)(NEt^(t)Bu)₂, (SiIH)(N^(i)Pr₂)₂, (SiIH)(N^(i)Pr^(t)Bu)₂, and(SiIH)(N^(t)Bu)₂. In some embodiments, a silicon precursor comprisestwo, three, four, five, six, seven, eight, nine, ten, eleven, twelve,thirteen, fourteen, fifteen or more compounds selected from(SiIH)(NH₂)₂, (SiIH)(NHMe)₂, (SiIH)(NHEt)₂, (SiIH)(NH^(i)Pr)₂,(SiIH)(NH^(t)Bu)₂, (SiIH)(NMe₂)₂, (SiIH)(NMeEt)₂, (SiIH)(NMe^(i)Pr)₂,(SiIH)(NMe^(t)Bu)₂, (SiIH)(NEt₂)₂, (SiIH)(NEt^(i)Pr)₂,(SiIH)(NEt^(t)Bu)₂, (SiIH)(N^(i)Pr₂)₂, (SiIH)(N^(i)Pr^(t)Bu)₂, and(SiIH)(N^(t)Bu)₂, and combinations thereof.

In some embodiments, a silicon precursor comprises one iodine, twohydrogens and one amine or alkylamine ligand bonded to silicon. In someembodiments silicon precursor comprises one or more of the following:(SiIH₂)NH₂, (SiIH₂)NHMe, (SiIH₂)NHEt, (SiIH₂)NH^(i)Pr, (SiIH₂)NH^(t)Bu,(SiIH₂)NMe₂, (SiIH₂)NMeEt, (SiIH₂)NMe^(i)Pr, (SiIH₂)NMe^(t)Bu,(SiIH₂)NEt₂, (SiIH₂)NEt^(i)Pr, (SiIH₂)NEt^(t)Bu, (SiIH₂)N^(i)Pr₂,(SiIH₂)N^(i)Pr^(t)Bu, and (SiIH₂)N^(t)Bu₂. In some embodiments a siliconprecursor comprises two, three, four, five, six, seven, eight, nine,ten, eleven, twelve, thirteen, fourteen, fifteen or more compoundsselected from (SiIH₂)NH₂, (SiIH₂)NHMe, (SiIH₂)NHEt, (SiIH₂)NH^(i)Pr,(SiIH₂)NH^(t)Bu, (SiIH₂)NMe₂, (SiIH₂)NMeEt, (SiIH₂)NMe^(i)Pr,(SiIH₂)NMe^(t)Bu, (SiIH₂)NEt₂, (SiIH₂)NEt^(i)Pr, (SiIH₂)NEt^(t)Bu,(SiIH₂)N^(i)Pr₂, (SiIH₂)N^(i)P^(i)Bu, (SiIH₂)N^(t)Bu₂, and combinationsthereof.

In some embodiments, a silicon precursor comprises one iodine and threeamine or alkylamine ligands bonded to silicon. In some embodiments,silicon precursor comprises one or more of the following: (SiI)(NH₂)₃,(SiI)(NHMe)₃, (SiI)(NHEt)₃, (SiI)(NH^(i)Pr)₃, (SiI)(NH^(t)Bu)₃,(SiI)(NMe₂)₃, (SiI)(NMeEt)₃, (SiI)(NMe^(i)Pr)₃, (SiI)(NMe^(t)Bu)₃,(SiI)(NEt₂)₃, (SiI)(NEt^(i)Pr)₃, (SiI)(NEt^(t)Bu)₃, (SiI)(N^(i)Pr₂)₃,(SiI)(N^(i)Pr^(t)Bu)₃, and (SiI)(N^(t)Bu)₃. In some embodiments asilicon precursor comprises two, three, four, five, six, seven, eight,nine, ten, eleven, twelve, thirteen, fourteen, fifteen or more compoundsselected from (SiI)(NH₂)₃, (SiI)(NHMe)₃, (SiI)(NHEt)₃, (SiI)(NH^(i)Pr)₃,(SiI)(NH^(t)Bu)₃, (SiI)(NMe₂)₃, (SiI)(NMeEt)₃, (SiI)(NMe^(i)Pr)₃,(SiI)(NMe^(t)Bu)₃, (SiI)(NEt₂)₃, (SiI)(NEt^(i)Pr)₃, (SiI)(NEt^(t)Bu)₃,(SiI)(N^(i)Pr₂)₃, (SiI)(N^(i)Pr^(t)Bu)₃, (SiI)(N^(t)Bu)₃, andcombinations thereof.

In certain embodiments, a silicon precursor comprises two iodines,hydrogen and one amine or alkylamine ligand or two iodines and twoalkylamine ligands bonded to silicon and wherein amine or alkylamineligands are selected from amine NH₂—, methylamine MeNH—, dimethylamineMe₂N—, ethylmethylamine EtMeN—, ethylamine EtNH—, and diethylamineEt₂N—. In some embodiments silicon precursor comprises one or more ofthe following: (SiI₂H)NH₂, (SiI₂H)NHMe, (SiI₂H)NHEt, (SiI₂H)NMe₂,(SiI₂H)NMeEt, (SiI₂H)NEt₂, (SiI₂)(NH₂)₂, (SiI₂)(NHMe)₂, (SiI₂)(NHEt)₂,(SiI₂)(NMe₂)₂, (SiI₂)(NMeEt)₂, and (SiI₂)(NEt₂)₂. In some embodiments asilicon precursor comprises two, three, four, five, six, seven, eight,nine, ten, eleven, twelve or more compounds selected from (SiI₂H)NH₂,(SiI₂H)NHMe, (SiI₂H)NHEt, (SiI₂H)NMe₂, (SiI₂H)NMeEt, (SiI₂H)NEt₂, (SiI₂)(NH₂)₂, (SiI₂)(NHMe)₂, (SiI₂)(NHEt)₂, (SiI₂)(NMe₂)₂, (SiI₂)(NMeEt)₂,(SiI₂)(NEt₂)₂, and combinations thereof.

Other Types of Si-Precursors Containing I or Br

A number of suitable silicon precursors containing nitrogen, such asiodine or bromine substituted silazanes, or sulphur, may be used in thepresently disclosed thermal and plasma ALD processes. In someembodiments silicon precursors containing nitrogen, such as iodine orbromine substituted silazanes, may be used in the presently disclosedthermal and plasma ALD processes in which a film with desired quality isto be deposited, for example at least one of the desired WER, WERR,pattern loading effect or/and step coverage features described below.

At least some of the suitable iodine or bromine substituted siliconprecursors may have the following general formula:H_(2n+2−y−z−w)Si_(n)(EH)_(n−1)X_(y)A_(z)R_(w)  (25)

-   -   wherein, n=2-10, y=1 or more (and up to 2n+2−z−w), z=0 or more        (and up to 2n+2−y−w), w=0 or more (and up to 2n+2−y−z), X is I        or Br, E is N or S, preferably N, A is a halogen other than X, R        is an organic ligand and can be independently selected from the        group consisting of alkoxides, alkylsilyls, alkyl, substituted        alkyl, alkylamines and unsaturated hydrocarbon; preferably n=2-5        and more preferably n=2-3 and most preferably 1-2. Preferably R        is a C₁-C₃ alkyl ligand, such as methyl, ethyl, n-propyl or        isopropyl.

At least some of the suitable iodine or bromine substituted silazaneprecursors may have the following general formula:H_(2n+2−y−z−w)Si_(n)(NH)_(n−1)X_(y)A_(z)R_(w)  (26)

-   -   wherein, n=2-10, y=1 or more (and up to 2n+2−z−w), z=0 or more        (and up to 2n+2−y−w), w=0 or more (and up to 2n+2−y−z), X is I        or Br, A is a halogen other than X, R is an organic ligand and        can be independently selected from the group consisting of        alkoxides, alkylsilyls, alkyl, substituted alkyl, alkylamines        and unsaturated hydrocarbon; preferably n=2-5 and more        preferably n=2-3 and most preferably 2. Preferably R is a C₁-C₃        alkyl ligand, such as methyl, ethyl, n-propyl or isopropyl.

In some embodiments, the silicon precursor comprises Si-compound, suchas heterocyclic Si compound, which comprises I or Br. Such cyclicprecursors may comprise the following substructure:—Si-E-Si—  (27)

-   -   wherein E is N or S, preferably N.

In some embodiments the silicon precursor comprises substructureaccording to formula (27) and example of this kind of compounds is forexample, iodine or bromine substituted cyclosilazanes, such iodine orbromine substituted cyclotrisilazane.

In some embodiments, the silicon precursor comprises Si-compound, suchas silylamine based compound, which comprises I or Br. Such silylaminebased Si-precursors may have the following general formula:(H_(3−y−z−w)X_(y)A_(z)R_(w)Si)₃—N  (28)

-   -   wherein, y=1 or more (and up to 3−z−w), z=0 or more (and up to        3−y−w), w=0 or more (and up to 3−y−z), X is I or Br, A is a        halogen other than X, R is an organic ligand and can be        independently selected from the group consisting of alkoxides,        alkylsilyls, alkyl, substituted alkyl, alkylamines and        unsaturated hydrocarbon. Preferably R is a C₁-C₃ alkyl ligand,        such as methyl, ethyl, n-propyl or isopropyl. Each of the three        H_(3−y−z−w)X_(y)A_(z)R_(w)Si ligands can be independently        selected from each other.        N Precursors

According to some embodiments, the second reactant or nitrogen precursorin a thermal ALD process may be NH₃, N₂H₄, or any number of othersuitable nitrogen compounds having a N—H bond.

FIG. 4 is a flow chart generally illustrating a silicon nitride thermalALD deposition cycle that can be used to deposit a silicon nitride thinfilm in accordance with some embodiments. According to certainembodiment, a silicon nitride thin film is formed on a substrate by anALD-type process comprising multiple silicon nitride deposition cycles,each silicon nitride deposition cycle 400 comprising:

(1) contacting a substrate with a vaporized silicon precursor 410 suchthat the silicon compound adsorbs on the substrate surface;

(2)removing excess silicon precursor and any byproducts 420;

(3) contacting the substrate with a nitrogen precursor 430; and

(4)removing excess nitrogen precursor and reaction byproducts 440.

The contacting steps are repeated 450 until a thin film of a desiredthickness and composition is obtained. As mentioned above, in someembodiments the substrate may be contacted simultaneously with thesilicon compound and the nitrogen precursor, while in other embodimentsthese reactants are provided separately.

According to some embodiments, a silicon nitride thin film is depositedusing a thermal ALD process on a substrate having three-dimensionalfeatures, such as in a FinFET application. The process may comprise thefollowing steps, not necessarily performed in this order:

(1) a substrate is loaded into a reaction space;

(2) a silicon-containing precursor, such as H₂SiI₂, is introduced intothe reaction space so that the silicon-containing precursor is adsorbedto a surface of the substrate;

(3) removing excess silicon-containing precursor and reaction byproductsare removed, such as by purging;

(4) a nitrogen-containing precursor, such as NH₃ or N₂H₄, is introducedinto the reaction space to react with the silicon-containing precursoron the substrate;

(5) removing excess nitrogen-containing precursor and reactionbyproducts, such as by purging; and

(6) steps (2) through (5) may be repeated until a silicon nitride filmof a desired thickness is formed.

In some embodiments, the ALD process is performed at a temperaturebetween about 100° C. to about 800° C. or between about 200° C. andabout 600° C. or between about 300° C. to about 500° C. In someapplications, the reaction temperature is about 400° C.

SiN Film Characteristics

Silicon nitride thin films deposited according to some of theembodiments discussed herein (irrespective of whether the siliconprecursor contained bromine or iodine) may achieve impurity levels orconcentrations below about 3 at-%, preferably below about 1 at-%, morepreferably below about 0.5 at-%, and most preferably below about 0.1at-%. In some thin films, the total impurity level excluding hydrogenmay be below about 5 at-%, preferably below about 2 at-%, morepreferably below about 1 at-%, and most preferably below about 0.2 at-%.And in some thin films, hydrogen levels may be below about 30 at-%,preferably below about 20 at-%, more preferably below about 15 at-%, andmost preferably below about 10 at-%.

In some embodiments, the deposited SiN films do not comprise anappreciable amount of carbon. However, in some embodiments a SiN filmcomprising carbon is deposited. For example, in some embodiments an ALDreaction is carried out using a silicon precursor comprising carbon anda thin silicon nitride film comprising carbon is deposited. In someembodiments a SiN film comprising carbon is deposited using a precursorcomprising an alkyl group or other carbon-containing ligand. In someembodiments a silicon precursor of one of formulas (9)-(28) andcomprising an alkyl group is used in a PEALD or thermal ALD process, asdescribed above, to deposit a SiN film comprising carbon. Differentalkyl groups, such as Me or Et, or other carbon-containing ligands mayproduce different carbon concentrations in the films because ofdifferent reaction mechanisms. Thus, different precursors can beselected to produce different carbon concentration in deposited SiNfilms. In some embodiments the thin SiN film comprising carbon may beused, for example, as a low-k spacer. In some embodiments the thin filmsdo not comprise argon.

FIGS. 5A-5B show FESEM images of various silicon nitride thin filmsdeposited according to the present disclosure. After the films weredeposited, they were HF-dipped for 2 minutes. FIGS. 6A-6C show the samesilicon nitride films after the dHF drip process. Uniform etching can beseen.

According to some embodiments, the silicon nitride thin films mayexhibit step coverage and pattern loading effects of greater than about50%, preferably greater than about 80%, more preferably greater thanabout 90%, and most preferably greater than about 95%. In some casesstep coverage and pattern loading effects can be greater than about 98%and in some case about 100% (within the accuracy of the measurement toolor method). These values can be achieved in aspect ratios of more than2, preferably in aspect ratios more than 3, more preferably in aspectratios more than 5 and most preferably in aspect ratios more than 8.

As used herein, “pattern loading effect” is used in accordance with itsordinary meaning in this field. While pattern loading effects may beseen with respect to impurity content, density, electrical propertiesand etch rate, unless indicated otherwise the term pattern loadingeffect when used herein refers to the variation in film thickness in anarea of the substrate where structures are present. Thus, the patternloading effect can be given as the film thickness in the sidewall orbottom of a feature inside a three-dimensional structure relative to thefilm thickness on the sidewall or bottom of the three-dimensionalstructure/feature facing the open field. As used herein, a 100% patternloading effect (or a ratio of 1) would represent about a completelyuniform film property throughout the substrate regardless of featuresi.e. in other words there is no pattern loading effect (variance in aparticular film property, such as thickness, in features vs. openfield).

In some embodiments, silicon nitride films are deposited to athicknesses of from about 3 nm to about 50 nm, preferably from about 5nm to about 30 nm, more preferably from about 5 nm to about 20 nm. Thesethicknesses can be achieved in feature sizes (width) below about 100 nm,preferably about 50 nm, more preferably below about 30 nm, mostpreferably below about 20 nm, and in some cases below about 15 nm.According to some embodiments, a SiN film is deposited on athree-dimensional structure and the thickness at a sidewall may beslightly even more than 10 nm.

According to some embodiments silicon nitride films with various wetetch rates (WER) may be deposited. When using a blanket WER in 0.5% dHF(nm/min), silicon nitride films may have WER values of less than about5, preferably less than about 4, more preferably less than about 2, andmost preferably less than about 1. In some embodiments it could lessthan about 0.3.

The blanket WER in 0.5% dHF (nm/min) relative to the WER of thermaloxide may be less than about 3, preferably less than about 2, morepreferably less than about 1, and most preferably less than about 0.5.

And in some embodiments, the sidewall WER of the three dimensionalfeature, such as fin or trench relative to the top region WER of a threedimensional feature, such as fin or trench, may be less than about 4,preferably less than about 3, more preferably less than about 2, mostpreferably about 1.

It has been found that in using the silicon nitride thin films of thepresent disclosure, thickness differences between top and side may notbe as critical for some applications, due to the improved film qualityand etch characteristics. Nevertheless, in some embodiments, thethickness gradient along the sidewall may be very important tosubsequent applications or processes.

In some embodiments, the amount of etching of silicon nitride filmsaccording to the present disclosure may be about one or two times lessthan amount of etching observed for thermal SiO₂ (TOX) in a 0.5% HF-dipprocess (for example in a process in which about 2 to about 3 nm TOX isremoved, one or two times less SiN is removed when deposited accordingto the methods disclosed herein). The WER of preferred silicon nitridefilms may be less than that of prior art thermal oxide films.

Specific Contexts for Use of SiN Films

The methods and materials described herein can provide films withincreased quality and improved etch properties not only for traditionallateral transistor designs, with horizontal source/drain (S/D) and gatesurfaces, but can also provide improved SiN films for use onnon-horizontal (e.g., vertical) surfaces, and on complexthree-dimensional (3D) structures. In certain embodiments, SiN films aredeposited by the disclosed methods on a three-dimensional structureduring integrated circuit fabrication. The three-dimensional transistormay include, for example, double-gate field effect transistors (DG FET),and other types of multiple gate FETs, including FinFETs. For example,the silicon nitride thin films of the present disclosure may be usefulin nonplanar multiple gate transistors, such as FinFETs, where it may bedesirable to form silicide on vertical walls, in addition to the tops ofthe gate, source, and drain regions.

Another 3D structure for which the SiN deposition techniques taughtherein are particularly useful is a 3D elevated source/drain structure,as taught in U.S. Patent Publication No. 2009/0315120 A1 by Shifren etal., the disclosure of which is incorporated herein by reference in itsentirety. Shifren et al. teach elevated source/drain structures thatinclude vertical sidewalls.

Example 1

A silicon nitride thin film was deposited at 400° C. according to thepresent disclosure by a PEALD process using H₂SiI₂ as the silaneprecursor and H₂+N₂ plasma as the nitrogen precursor. This filmexhibited a combination of some of the best qualities of both ALDreaction types: the typical high quality of PEALD SiN films and theisotropic etch behavior of thermal ALD films. While these results arenot fully understood, the film properties and etch behavior werenevertheless within the specs for the high quality spacer layerapplication.

For this application, the step coverage and pattern loading effect on atrench structure with an aspect ratio of 2 should be over 95%, the wetetch rate (WER) should be less than 50% of the WER of thermally oxidizedsilicon (SiO₂, TOX), and the etch rate should be about the same onhorizontal and vertical walls of the trench structure. Finally, thegrowth rate should be over 0.5 nm/min and impurity contents as low aspossible.

At 400° C. the film growth rate was 0.52 Å/cycle, and the thicknessnon-uniformity 6.2% (1-σ). The refractive index was 2.04 with anon-uniformity of 0.7% (1-σ). The growth rate per minute was not yetoptimized and was 0.13 nm/min.

The wet etch rate of a planar film was 1.13 nm/minute, which is 46.7% ofthe WER of Tox (2.43 nm/min). On a trench structure the filmconformality was from about 91.0 to about 93.1% and the pattern loadingeffect from about 95.7 to about 99.3% % as deposited (before etching).After a 2 minute dilute (0.5%) HF etch, the conformality value was fromabout 91.5 to about 94.6% and the pattern loading effect from about 97.4to about 99.5% %. The wet etch rate top region of the trench was A 4.32nm/min, B 2.98 nm/min on the trench sidewall and C 3.03 nm/min on trenchbottom. The field areas showed D 2.63 nm/min etch rate.

Without being tied to any particular theory, it is believed that itcould be beneficial that the ligand removal step of iodine or bromine iscompleted before the plasma discharge. That can avoid leftover ligandsfrom decomposing and re-entering the film as impurities, and in the caseof halides, the formation of plasma activated halides is also avoided.

The composition of a silicon nitride thin film deposited according tothe present disclosure was analyzed by HFS-RBS. The results are shown inTable 1 below. Additionally, XRR data was obtained of the same film. Thethickness of the film was determined to be about 117 nm. The massdensity was determined to be 2.63 (±0.1) g/cm³. And the surface RMSroughness was determined to be 1.76 (±0.1) nm.

TABLE 1 Film composition measured by HFS-RBS. Element Amount/atom-%Uncertainty/atom-% Si 32.7 1 N 48.9 3 H 18.3 2 Combined impurities ~0.150.15 Max. individual impurity 0.1 0.1Example 2

Silicon nitride thin film with improved etch properties and impuritycontent (compared to example 1) were deposited in a direct plasma ALDshowerhead reactor by PEALD processes according to the presentdisclosure. Susceptor temperatures of 200° C. and 400° C. were used.H₂SiI₂ was used as the silicon precursor and H₂+N₂ plasma was used asthe nitrogen precursor. Plasma power was from about 200 W to about 220 Wand the gap between the showerhead plate and susceptor (i.e. the spacewhere plasma is generated) was 10 mm. The plasma did not contain Ar.Nitrogen was used as a carrier gas and was flowed throughout thedeposition process. H₂SiI₂ consumption was about 9.0 mg/cycle.

At 400° C. the films growth rate was 0.7 Å/cycle and the deposited filmswere conformal. The refractive indexes were 1.92-1.93. The wet etchrates (WER) of planar films in 100:1 dHF were from about 20 to 30% ofthe WER of thermal oxide (SiO₂). On a trench structure the film wet etchrate ratio of trench sidewall to trench top varied from about 0.8 toabout 1.0.

The impurity content of silicon nitride thin films deposited at 200° C.were analyzed by TXRF. Films contained 8.43×10¹² iodine atoms per cm²,which is slightly less than the impurity content (1.418×10¹³ iodineatoms per cm²) of films deposited using plasma containing Ar in additionto H₂+N₂ plasma. In addition, films deposited at 400° C. usingAr-containing plasma had Ar as an impurity (8.067×10¹³ argon atoms percm²) as evidenced by TXRF analysis. Without being tied to any particulartheory, it is believed that argon could be trapped inside the film andthat by using plasma that does not contain argon this can be avoided.

Plasma Treatment

As described herein, plasma treatment steps may be used in formation ofa variety of materials to enhance film properties. In particular,utilization of a plasma densification step, for example using a nitrogenplasma, may enhance the properties of nitride films, such as SiN films.In some embodiments, a process for forming SiN films comprisesdepositing the SiN and treating the deposited SiN with a plasmatreatment. In some embodiments, the SiN is deposited by a thermal ALDprocess, and subsequently subjected to a plasma treatment. For example,SiN may be deposited by a thermal ALD process comprising a plurality ofdeposition cycles comprising a first phase in which a substrate iscontacted with a silicon precursor such that silicon species areadsorbed onto a surface of the substrate, and a second phase in whichthe silicon species adsorbed onto the substrate surface are contactedwith a nitrogen precursor. As discussed herein, the SiN deposited by thethermal ALD process may be subject to a plasma treatment, for exampleafter each deposition cycle, at intervals during the deposition processor following completion of the SiN deposition process. In someembodiments, SiN is deposited by a PEALD process. In some embodiments, aPEALD deposition process comprises a first phase and a second phase. Forexample, a first phase of a SiN PEALD process may comprise contacting atarget substrate with a silicon precursor such that silicon species areadsorbed onto a surface of the target substrate and a second phase ofthe SiN PEALD process may comprise contacting the silicon speciesadsorbed onto the surface of the target substrate with a plasmacomprising nitrogen in order to form SiN. In this part of the depositionprocess, the plasma may comprise hydrogen ions. For example, a PEALDsilicon nitride deposition cycle may include contacting the targetsubstrate with a silicon precursor, such as those described herein, andan activated nitrogen precursor, for example a plasma of nitrogen andhydrogen gas. The target substrate may be exposed to activated hydrogencontaining species (e.g., H⁺ and/or H₃ ⁺ ions) in this step, which may,for example, facilitate the surface reactions. However, it has beenfound that while exposure of silicon nitride film to activated hydrogencontaining species may facilitate deposition of silicon nitride films(e.g., facilitate one or more surface reactions for conformal depositionof silicon nitride films), such exposure may result in formation of oneor more defects, such as delamination of the film and/or formation ofblister defects in the silicon nitride film. Thus, in some embodimentsthe first plasma step in the PEALD silicon nitride deposition cycle(also referred to as a nitrogen plasma precursor step) is carried out ata plasma power and duration that is low enough to avoid significantdefect formation or delamination.

In some embodiments, subsequent to deposition of SiN by PEALD, a secondplasma treatment step is carried out. The second plasma treatment stepmay be carried out after each PEALD cycle, at intervals during SiNdeposition, or after the PEALD SiN deposition process is complete. Thesecond plasma treatment step may be a nitrogen plasma treatment step.The second plasma step may, for example, lead to densification of thedeposited SiN film or otherwise improve film properties. Thus, thesecond nitrogen plasma treatment step may also be referred to as adensification step. The plasma power and/or duration may be greater inthe densification step (second nitrogen plasma treatment step) than inthe first nitrogen plasma precursor step, as discussed in more detailbelow. Importantly, the second nitrogen plasma treatment step does notinclude provision of energetic hydrogen species, such as H⁺ or H₃ ⁺. Thedensification step may be carried out after every cycle of a PEALDprocess, or after various intervals of the PEALD deposition process, asdiscussed in more detail below.

Thus, in some embodiments, one or more silicon nitride film depositioncycles can be followed by a nitrogen plasma treatment. Utilizing thenitrogen plasma treatment may facilitate formation of silicon nitridefilms having certain desired characteristics while reducing or avoidingformation of defects such as silicon nitride film delamination and/orformation of blister defects in the silicon nitride film. Use of anitrogen plasma treatment may allow for the use of activated hydrogencontaining species in the deposition of the silicon nitride films forconformal deposition of silicon nitride films, while obtaining a filmthat exhibits desired characteristics such as desired wet etch rates(e.g., wet etch rates in dilute HF), and without introducing significantdefects in the film. Without being limited by any particular theory ormode of operation, application of a nitrogen plasma treatment mayincrease a density of the silicon nitride film formed by the siliconnitride film deposition cycles. In some embodiments, application of anitrogen plasma treatment can facilitate formation of a silicon nitridefilm which demonstrates increased resistance to wet etch (e.g., ascompared to silicon nitride films formed without a nitrogen plasmatreatment, in which the top layer may be easily oxidized and demonstratesimilar WERR as that of thermal silicon oxide). In some embodiments,application of a nitrogen plasma treatment can facilitate formation of asilicon nitride film having increased etch rate uniformity of horizontalsurfaces relative to vertical surfaces on 3-D features, decreased wetetch rate (WER), and/or decreased wet etch rate ratio (WERR) relative tothermal oxide (TOX).

In some embodiments, a silicon nitride thin film formed on 3-D featuresaccording to one or more processes described herein can demonstrate aratio of a wet etch rate (WER) of the silicon nitride thin film on thesidewalls of the 3-D features to a wet etch rate (WER) of the siliconnitride thin film on the top regions of the 3-D features of less thanabout 1 in 0.5% dHF. In some embodiments, the ratio is about 0.75 toabout 1.5 in 0.5% dHF, and in some embodiments may be about 0.9 to about1.1.

In some embodiments, utilizing a nitrogen plasma treatment mayfacilitate formation of silicon nitride films useful in applicationssuch as sacrificial layers, gate spacers and/or spacer defineddouble/quadruple patterning (SDDP/SDQP) in state-of-the-artsemiconductor devices such as FiNFETs and other multigate transistors.

Although embodiments described herein refer to PEALD deposition ofsilicon nitride films, it will be understood that other depositiontechniques may also be applicable (e.g., thermal ALD, and/or radicalenhanced ALD). Further, the nitrogen plasma treatment may be applied tothe deposition of other materials (e.g., metallic materials, dielectricmaterials, and/or other nitride materials, such as titanium nitride(TiN)).

FIG. 7 is a flow chart 700 generally illustrating an example of asilicon nitride film formation process 770 comprising a silicon nitridePEALD deposition process 760 followed by a nitrogen plasma treatment 740in accordance with some embodiments. As described herein, a siliconnitride film deposition process 760 can include one or more cycles 730of contacting a target substrate with one or more silicon precursors 710(e.g., a silicon precursor step), followed by contacting the targetsubstrate with one or more nitrogen precursors 720 (e.g., a nitrogenprecursor step). In some embodiments the nitrogen precursor is anitrogen plasma that may include activated hydrogen species.

Exposing the target substrate to a nitrogen plasma treatment 740 canfollow one or more cycles 730 of contacting a target substrate with oneor more silicon precursors 710 and contacting the target substrate withone or more nitrogen precursors 720. The nitrogen plasma treatment 740can be carried out after each deposition cycle 730, or intermittentlythroughout the deposition process, for example every 2, 3, 4, 5, 6, 7etc. . . . cycles.

In some embodiments, the silicon nitride deposition process 760 isfollowed by exposing the target substrate to a nitrogen plasma treatment740 and that process is repeated 750 a number of times. For example, acomplete silicon nitride film formation process 770 can include a numberof cycles 730 of contacting a target substrate with one or more siliconprecursors 710 and contacting the target substrate with one or morenitrogen precursors 720, followed by exposing the target substrate to anitrogen plasma treatment 740.

According to certain embodiments, a process for forming a siliconnitride film on a substrate in a reaction space comprises a number ofrepetitions of the following steps:

(1) a silicon-containing precursor, such as SiI₂H₂, is introduced intothe reaction space so that silicon-containing species is adsorbed to asurface of the substrate;

(2) excess silicon-containing precursor and/or reaction byproducts areremoved from the reaction space, if any;

(3) a nitrogen-containing precursor, such as N₂, NH₃, N₂H₄, or N₂ andH₂, is introduced into the reaction space;

(4) generating reactive species from the nitrogen precursor;

(5) contacting the substrate with the reactive species; and

(6) removing excess nitrogen atoms, plasma, or radicals and/or reactionbyproducts, if any;

(7) applying to the substrate a nitrogen plasma treatment

Steps (1) through (6) may be repeated until a silicon nitride film of adesired thickness is formed.

In some embodiments, step (6) is not performed prior to application ofthe nitrogen plasma treatment. For example, contacting the substratewith reactive species generated from the nitrogen precursor may befollowed by application of the nitrogen plasma treatment without orsubstantially without a purge process, such that a residual amount ofone or more reactive species from the nitrogen precursor step may bepresent in the nitrogen plasma treatment. For example, a residual amountof hydrogen species may be present.

In some embodiments steps (4) and (5) are replaced by a step in whichthe nitrogen atoms, plasma or radicals are formed remotely and providedto the reaction space.

FIG. 8 is a flow chart 800 generally illustrating another example of asilicon nitride film formation process 870 comprising a silicon nitridePEALD deposition process 860 followed by a nitrogen plasma treatment 840in accordance with some embodiments. As described herein, a siliconnitride film deposition process 860 can include one or more cycles 830of contacting a target substrate with one or more silicon precursors 810followed by contacting the target substrate with a nitrogen plasmacomprising activated hydrogen containing species (e.g., as part of astep for contacting the substrate with one or more nitrogen precursors)820.

Contacting the target substrate with a nitrogen plasma free orsubstantially free of activated hydrogen containing species (e.g., as apart of a nitrogen plasma treatment) 840 can follow one or more cycles830 of contacting the target substrate with the one or more siliconprecursors 810 and contacting the target substrate with the nitrogenplasma comprising activated hydrogen containing species 820. Contactingthe target substrate with the nitrogen plasma free or substantially freeof activated hydrogen containing species 840 can be carried out aftereach deposition cycle 830, or intermittently throughout the depositionprocess, for example every 2, 3, 4, 5, 6, 7 etc. . . . cycles.

In some embodiments, the silicon nitride deposition process 860 followedby contacting the target substrate with a nitrogen plasma that is freeor substantially free of activated hydrogen species 840 can be repeated850 a number of times. For example, a complete silicon nitride filmformation process 870 can include a number of cycles of the siliconnitride deposition process 860 followed by contacting the targetsubstrate with a nitrogen plasma free or substantially free of activatedhydrogen containing species 840.

As described herein, the PEALD process may be performed at a temperaturebetween about 200° C. to about 400° C., between about 300° C. and about400° C., or at about 400° C.

In some embodiments, the nitrogen plasma treatment can comprisecontacting the substrate with a plasma formed from a reactant thatincludes nitrogen and one or more inert gases. For example, the nitrogenplasma treatment can include contacting the substrate with a plasmaformed from nitrogen (N₂) and one or more noble gases, such as argon(Ar). The nitrogen plasma treatment may comprise a direct plasmaprocess. For example, one or more cycles of a PEALD silicon nitridedeposition process may be followed by a nitrogen plasma treatment. Oneor more cycles of a PEALD silicon nitride deposition process comprisinga plasma nitrogen precursor step can be combined with a nitrogen plasmatreatment to facilitate formation of a conformal silicon nitride filmhaving desired chemical and/or physical properties (e.g., desired wetetch characteristics and free or substantially free from delaminationdefects).

In some embodiments, the nitrogen plasma treatment does not include asignificant quantity of activated hydrogen containing species (e.g.,hydrogen ions (H⁺)). In some embodiments, the nitrogen plasma treatmentcan be free or substantially free of activated hydrogen containingspecies. In some embodiments, the nitrogen treatment can include aresidual amount of activated hydrogen containing species remaining froma previous process performed in the reaction chamber, such as from acycle in a silicon nitride deposition process for contacting the targetsubstrate with nitrogen precursors (e.g., a nitrogen precursor step). Asdescribed herein, in some embodiments a purge process may not beperformed prior to the nitrogen plasma treatment, such that some amountof hydrogen containing species remains in the reaction chamber. Forexample, the nitrogen plasma treatment may not supply a hydrogencontaining component to the reaction chamber but some quantity ofhydrogen containing species from a previous process step may remain inthe process chamber during at least a portion of the nitrogen plasmatreatment.

In some embodiments, plasma power in a PEALD process for depositingsilicon nitride is sufficiently low to reduce or avoid formation of filmdefects and/or delamination. However, the plasma power may be higher inthe nitrogen plasma treatment. Thus, in some embodiments, a plasma powerused in a nitrogen plasma treatment is greater than or equal to thatused in a PEALD process for depositing silicon nitride (e.g., a nitrogenprecursor step of the PEALD process). For example, in a PEALD cycle forforming SiN, a plasma may be formed with a gas comprising nitrogen andhydrogen using a reduced plasma power, while in a nitrogen plasmatreatment free of or comprising only a residual amount of hydrogencontaining species, a relatively higher plasma power may be used. Insome embodiments, a plasma power applied during the nitrogen plasmatreatment is up to about 900% that of a plasma power applied during aPEALD process for forming SiN where activated hydrogen species areformed (e.g., during a nitrogen precursor step of the PEALD process). Insome embodiments, a plasma power for the nitrogen plasma treatment ispreferably up to about 400% that of the plasma power used in thenitrogen precursor step, more preferably about 100% to about 250% thatof the plasma power used in the nitrogen precursor step, and mostpreferably about 100% to about 200% that of the plasma power used in thenitrogen precursor step.

In some embodiments, a plasma power used in a nitrogen plasma treatmentis less than that used in a nitrogen precursor step. For example, aplasma power used in the nitrogen plasma treatment can be between about50% and 100% of a plasma power used in the nitrogen precursor step.

Plasma power used in a PEALD silicon nitride deposition process candepend on various factors, including a geometry of structures and/ormaterial of the target substrate on which the silicon nitride isdeposited. As described herein, plasma power used in a cycle of PEALDsilicon nitride deposition may be about 50 Watts (W) to about 600 W(e.g., in a reaction chamber configured for processing a 300 millimeter(mm) wafer substrate), including for example from about 100 W to about300 W, and from about 150 W to about 250 W. As described herein, aplasma power applied during a nitrogen plasma treatment may be greaterthan or equal to a plasma power applied during the nitrogen precursorstep, including for example, about 100 W to about 1000 W, preferablyabout 125 W to about 600 W, more preferably about 150 W to about 300 W.In some embodiments, a power density of a plasma applied during anitrogen plasma treatment (e.g., in a reaction chamber configured forprocessing a 300 millimeter (mm) wafer substrate) can be about 0.07Watts per cubic centimeter (W/cm³) to about 70 W/cm³, preferably about0.08 W/cm³ to about 0.4 W/cm³, and more preferably about 0.1 W/cm³ toabout 0.2 W/cm³.

A duration of the nitrogen plasma treatment can be selected to obtaindesired results. In some embodiments the duration is based, in part, ona thickness of the silicon nitride film being treated. For example, ashorter nitrogen plasma treatment can be used in the nitrogen plasmatreatment applied after each PEALD cycle, while a longer nitrogen plasmatreatment can be used when the nitrogen plasma treatment is applied lessfrequently.

As described herein, a silicon nitride formation process may include aplurality of deposition cycles for depositing the silicon nitride filmand one or more nitrogen plasma treatments steps, where each depositioncycle can include a silicon precursor step followed by a nitrogenprecursor step. In some embodiments, a cycle including a plurality ofdeposition cycles (e.g., a deposition cycle including a siliconprecursor step followed by nitrogen precursor step) and one or morenitrogen plasma treatment steps, can be repeated a number of times. Insome embodiments, a plurality of deposition cycles can be repeated toachieve a desired silicon nitride film thickness, which then can befollowed by one or more nitrogen plasma treatment steps.

In some embodiments, a total duration of the nitrogen precursor steps inPEALD silicon nitride film deposition is greater than or equal to thetotal duration of the nitrogen plasma treatments. A total duration ofthe nitrogen plasma treatment can be a sum of the lengths of allnitrogen plasma treatments performed in the silicon nitride filmformation process, and a total duration of the nitrogen precursor stepcan be the sum all lengths of nitrogen precursor steps performed in thesilicon nitride film formation process.

A duration of nitrogen precursor steps (e.g., plasma processes includingactivated hydrogen species, such as H⁺ ions) may be selected to achievedesired film growth and/or desired conformal deposition of the film,while reducing or avoiding formation of film defects (e.g., blisterdefects). In some embodiments, a duration of a nitrogen precursor stepcan depend on a magnitude of the plasma power used in the nitrogenprecursor step, and/or a duration in which the plasma power is applied.In some embodiments, a larger plasma power may be applied for a shorterduration to facilitate formation of silicon nitride films without orsubstantially without blistering and/or delamination. For example,without being limited to any particular theory or mode of operation, anincrease in plasma power applied and/or duration of the nitrogenprecursor step, may contribute to formation of film defects such asblistering and/or delamination. For example, a 6 seconds plasma durationfor a nitrogen precursor step at a power of about 200 W may produce noor substantially no blisters, while a 8 seconds duration with the sameplasma power of about 200 W has may result in formation of blisters. Forexample, a 6 seconds plasma duration at a power of about 400 W mayresult in formation of blisters.

In some embodiments, a nitrogen precursor step comprising hydrogen canhave a plasma energy in Watts (W) multiplied by the plasma duration inseconds (s) of less than about 5000 W*s, preferably less than about 2500W*s and most preferably less than about 1000 W*s.

In some embodiments, a nitrogen plasma treatment of a silicon nitridedeposition process can have a total duration of about 1% to about 100%the total duration in which activated hydrogen containing species areprovided in the nitrogen precursor step, preferably about 5% to about75% that of the total duration in which activated hydrogen containingspecies are provided of in the nitrogen precursor step, and morepreferably about 10% to about 50%.

In one embodiment, a nitrogen plasma treatment of a silicon nitridedeposition process can have a total duration of about 40% of the totalduration of the nitrogen precursor step in which activated hydrogencontaining species are provided. For example, a silicon nitridedeposition process can include twenty-five cycles of a silicon precursorstep followed by a nitrogen precursor step, each cycle including 6seconds of the nitrogen precursor step in which activated hydrogencontaining species are provided, providing a silicon nitride processincluding 150 seconds total of nitrogen precursor steps in whichactivated hydrogen containing species are provided. The total durationof the nitrogen plasma treatment that is 40% of the nitrogen precursorstep in which activated hydrogen containing species are provided can beabout 60 seconds.

The frequency with which the target substrate is exposed to the nitrogenplasma treatment can be selected to achieve desired final filmcharacteristics. For example, one or more nitrogen plasma treatments canfollow a number of repetitions of cycles in which the target substrateis exposed to one or more silicon precursors followed by nitrogenprecursors for silicon nitride film growth. In some embodiments, cyclesof exposing the target substrate to one or more silicon precursorsfollowed by nitrogen precursors can be repeated twenty-five times,before each nitrogen plasma treatment. For example, a nitrogen plasmatreatment can follow every repetition of twenty-five cycles of exposingthe target substrate to one or more silicon precursors followed bynitrogen precursors. In some embodiments, a nitrogen plasma treatmentcan follow every repetition of fifty cycles of exposing the targetsubstrate to one or more silicon precursors followed by nitrogenprecursors. In some embodiments, a nitrogen plasma treatment can followevery repetition of one hundred cycles of exposing the target substrateto one or more silicon precursors followed by nitrogen precursors.

Without being limited by any particular theory or mode of operation, aplasma nitrogen treatment can be applied for densification of thesilicon nitride film, such as through ion bombardment of the siliconnitride film. For example, increased exposure of the silicon film to theplasma during the nitrogen plasma treatment can increase the dose of ionbombardment, increasing the film densification. A nitrogen plasmatreatment free or substantially free of hydrogen may facilitate use ofincreased plasma power while facilitating formation of silicon nitridefilms without or substantially without delamination defects. Meanwhile,hydrogen containing species may be used in a silicon nitride growthcycle to facilitate surface reactions and/or conformal deposition of thesilicon nitride film. A densified silicon nitride film can demonstratedecreased wet etch rate and/or increased wet etch uniformity, includingfor example increased uniformity in etch rates of features on a verticalsurface and horizontal surface of 3-D features.

In some embodiments, a process for providing —NH surface functionalgroups can be performed subsequent to a nitrogen plasma treatment.Without being limited by any particular theory or mode of operation, aquantity of —NH surface functional groups for silicon nitride filmgrowth may be removed by ion bombardment of the target substrate surfaceoccurring during a nitrogen plasma treatment. A process for providing—NH surface functional groups can be performed subsequent to a nitrogenplasma treatment to provide the target substrate surface —NH functionalgroups which have been removed during the nitrogen plasma treatment. Insome embodiments, the process for providing the surface —NH functionalgroups can comprise a plasma process, and one or more nitrogencontaining and hydrogen containing components. In some embodiments, aprocess for providing surface —NH groups can be the same as a processfor providing nitrogen precursors. For example, the plasma process forproviding —NH surface functional groups can comprise exposing the targetsubstrate to plasma generated in nitrogen containing gas. In someembodiments, the plasma may contain hydrogen as well, such as to provideactivated hydrogen containing and nitrogen containing species. Forexample, a process similar to or the same as a nitrogen precursor stepof a PEALD silicon nitride process can be performed subsequent to anitrogen plasma treatment for providing —NH surface functional groups.

Examples of Nitrogen Treatment Process Combined with PEALD SiliconNitride Deposition

Example 1

Two examples of a cycle of silicon nitride film formation processes areprovided below. Each process includes a combination of a PEALD siliconnitride deposition process with a nitrogen plasma treatment, and wetetch performance of silicon nitride films formed using each sequence isgraphed in FIG. 9, as discussed below.

Example a)

A cycle of a silicon nitride film formation process included exposing atarget substrate to plasma for a total of 18 seconds: exposing a targetsubstrate for 2 seconds to a silicon precursor, followed by exposing thetarget substrate for 6 seconds to plasma generated for nitrogenprecursors by nitrogen (N₂) and hydrogen (H₂) at a power of about 50 W,followed by exposing the target substrate for 6 seconds to a plasmagenerated by nitrogen (N₂) and argon (Ar) for a nitrogen plasmatreatment at a plasma power of about 200 W, and followed by exposing thetarget substrate for 6 seconds to the plasma generated from nitrogen(N₂) and hydrogen (H₂) at a plasma power of about 50 W (e.g., forproviding —NH surface functional groups to the target substratesurface).

Example b)

A cycle of a silicon nitride film formation process included exposing atarget substrate to plasma for a total of 30 seconds: exposing a targetsubstrate for 2 seconds to a silicon precursor, followed by exposing thetarget substrate for 12 seconds to plasma generated for nitrogenprecursors using nitrogen (N₂) and hydrogen (H₂) at a power of about 50W, followed by exposing the target substrate for 6 seconds to a plasmagenerated by nitrogen (N₂) and argon (Ar) for a nitrogen plasmatreatment at a plasma power of about 200 W, and followed exposing thetarget substrate for 12 seconds to the plasma generated from nitrogen(N₂) and hydrogen (H₂) at a plasma power of about 50 W (e.g., forproviding —NH surface functional groups to the target substratesurface).

Each of the example cycles were repeated for a number of times to obtaina desired silicon nitride film thickness and achieve a silicon nitridefilm having desired properties. A purge process prior to performing thenitrogen plasma treatment and subsequent to the step for contacting thetarget substrate with the nitrogen precursor was omitted, while purgeprocesses were performed between silicon precursor and nitrogenprecursor steps.

It was found that silicon nitride film formed using cycles of bothexamples provided films free or substantially free of blister and/orfilm delamination defects. The silicon nitride film growth rate percycle for both examples was around 0.2 angstroms per cycle (Å/c),demonstrating that surface reaction for film growth was saturated forthe cycle including 12 seconds total of nitrogen (N₂) and hydrogen (H₂)50 W process. Without being limited by any theory or mode of operation,additional plasma exposure beyond that provided in Example a) maycontribute to densification of the silicon nitride film, rather thanadditional film growth.

FIG. 9 shows the wet etch rate (WER) in nanometers per minute (nm/min)and wet etch rate ratio (WERR) as compared to thermal silicon oxide(TOX), as a function of dipping time in dilute HF solution (dHF), inminutes (min), of two silicon nitride films formed using a plurality ofcycles of the sequences shown in Examples a) and b). The WER and WERRdata demonstrate that silicon nitride films formed using processes whichinclude a nitrogen plasma treatment can have superior WER (e.g., lessthan about 0.1 nm/min) and WERR (e.g., less than about 0.06). Such WERand WERR values can be about one order of magnitude lower than thatdemonstrated by silicon nitride films formed using the conventionalprocesses which do not include a nitrogen plasma treatment.

Example 2

FIG. 10 shows a test setup in a direct plasma reaction chamberconfigured to demonstrate film growth induced by ion bombardmentseparate from radical induced film growth. A silicon coupon having apolished surface facing away (e.g., shown as down in FIG. 10) from theplasma (e.g., a showerhead in the reaction chamber) can be mounted overa silicon wafer. A gap can be maintained between the silicon coupon andthe wafer. The gap can be varied between about 0.7 millimeters (mm) andabout 2.1 mm. For example, in such a setup, few or no ions can reach thepolished silicon coupon surface while radicals can diffuse to thepolished silicon coupon surface. A SiI₂H₂+N₂/H₂ PEALD silicon nitridedeposition process run using the test setup can grow film on the siliconcoupon surface facing down. This growth is believed to be caused mainlyby radicals, such as N*, H*, NH* and/or NH₂*. Film growth on thepolished silicon coupon surface can be measured to determine radicalinduced film growth.

FIG. 11 shows wet etch rate (WER) in nm/min and wet etch rate ratio(WERR) comparing wet etch rates of thermal silicon oxide to a siliconnitride film grown using a SiI₂H₂+N₂/H₂ PEALD process, where the siliconnitride film is grown on the polished surface of a silicon coupon in asetup shown in the experimental setup of FIG. 10. The gap between thesilicon wafer and the silicon coupon was about 1.4 mm. The resultsindicate a very uniform film quality although film initial thickness aredifferent which probably caused by radical flux reducing during thediffusing. FIG. 11 shows that the silicon nitride film grown on the Sicoupon with radical enhanced ALD can demonstrate uniform WER, indicatingfor example uniformity in the quality of the film. The inset in FIG. 11shows the silicon nitride film thickness before and after 30 seconds dHFwet etch. The film thickness across the coupon indicates that thesilicon nitride can be grown with only or substantially only radicalsusing SiI₂H₂ precursor, for example, due to high reactivity of SiI₂H₂.

When another silicon precursor, bis(trichlorosilyl)ethane, was usedinstead of SiI₂H₂, using the setup shown in FIG. 10, no film growth wasobserved on the polished silicon coupon surface. Film growth wasobserved only on upper surfaces of the silicon wafer exposed to thedirect ion bombardment. It can thus be concluded that SiI₂H₂ is a morereactive precursor than bis(trichlorosilyl)ethane and that radicalenhanced ALD is possible.

Example 3

As described herein, silicon nitride film quality may be improved byapplying increased process temperature, increased plasma power and/orlonger plasma pulse duration. However, increasing plasma power and/orplasma pulse duration, such as with plasma comprising activated hydrogencontaining species, may provide silicon nitride films demonstratingblister and/or delamination defects.

FIG. 12 shows formation of blister defects in silicon nitride films ofdifferent thicknesses in which the silicon nitride films were exposed tovarying doses of activated hydrogen species (e.g., H⁺ ion) in apost-hydrogen plasma treatment. The silicon nitride films were exposedto hydrogen plasma with different plasma powers and different durations,and the degree of blister defect formation on the respective siliconnitride films was observed. FIG. 12 shows top views of SiN films havingvarious thicknesses, by SEM, corresponding to the following processes:(1) 20 nm SiN+H₂ plasma 200 W for 30 min, (2) 20 nm SiN+H₂ plasma 200 Wfor 15 min, (3) 20 nm SiN+H₂ plasma 100 W for 30 min, (4) 10 nm SiN+H₂plasma 100 W for 30 min.

As shown in FIG. 12, increased blister defects, for example caused bysilicon nitride film delamination, can increase with increased plasmapower and/or dose of activated hydrogen species. Improving film quality,such as to reduce blister defects, may be facilitated by reducing filmbombardment by high energetic and high dose of activated hydrogenspecies.

Example 4

As described herein, frequency with which the nitrogen plasma treatmentis applied can be varied to achieve desired silicon nitride filmcharacteristics. Effects upon silicon nitride film characteristics ofnitrogen plasma treatment frequency was approximated by etching asilicon nitride film which was treated only once after film deposition,in which the one nitrogen plasma treatment was 30 minutes. FIG. 13Ashows the film thickness in nm as a function of dipping time in minutesin dilute HF (dHF), and FIG. 13B shows a wet etch rate ratio (WERR) ofthe film as compared to thermal silicon oxide (TOX) as a function ofdipping time in minutes in dilute HF (dHF). FIG. 13B shows that the etchrate of this film was very low in the first 4 minutes of etching timewhere approximately 1 nm was etched. After 10 minutes dip time the etchrate increased to the same level as a silicon nitride film which was notsubjected to a nitrogen plasma treatment. It can be concluded that atleast about 1 nm to about 2 nm of silicon nitride film can be madehighly etch resistant (e.g., a “skin effect”) using nitrogen plasmatreatment. In some embodiments, a “skin effect” of the nitrogentreatment process can be achieved to a depth of about 2 nm to about 3nm.

For example, with a growth rate of a silicon nitride deposition processcan be about 0.4 Å/cycle, 25 to 50 cycles of silicon nitride filmdeposition can be applied to deposit about 1 nm to about 2 nm of film. Afrequency at which a nitrogen plasma treatment can be applied during asilicon nitride film formation process can be after about every 25^(th)to about every 50^(th) cycle of silicon nitride film deposition (e.g.,each cycle including a silicon precursor step followed by a nitrogenprecursor step), such that an etch rate in dHF of most or all of thesilicon nitride thickness can be decreased after application of thenitrogen plasma treatment.

In some embodiments, a frequency at which a nitrogen plasma treatmentcan be applied during a silicon nitride film formation process can beafter about at least every 100^(th) cycle of silicon nitride filmdeposition, preferably after at least every 50^(th) cycle and mostpreferably after at least every 25^(th) cycle.

In some embodiments, a thickness of the silicon nitride film formed isless than about 3 nm, preferably less than about 2 nm, and morepreferably less than about 1 nm, for example such that an etch rate ofmost or all of the silicon nitride film thickness can be improved afterbeing treated by a nitrogen plasma treatment. In some embodiments, asilicon nitride film thickness can be less than about 0.5 nm.

FIGS. 14A and 14B show film composition and dHF wet etch rate ratio(WERR), respectively, of the films processed using a one minute nitrogenplasma treatment after every 25th, 50th or 100th cycle of siliconnitride film deposition. FIG. 14A shows that the H content can besignificantly decreased when frequency in applying the nitrogen plasmatreatment is increased. Si and N contents remain approximately the same.The WERR increases when the number of cycles between nitrogen plasmatreatments increases. For example, 100 cycles of silicon nitride filmdeposition can correspond to about 4 nm of film deposition and there thetreatment is not as effective in reducing wet etch rate, as comparedwith nitrogen plasma treatments applied after about 1 nm and 2 nm filmdeposition, after every 25^(th) and 50^(th) cycles, respectively.

In some embodiments, a number of cycles between nitrogen plasmatreatments can be selected based on a trade-off between silicon nitridefilm etch properties and throughput. For example, while good etchproperties can be achieved with a nitrogen plasma treatment appliedafter every deposition cycle but will significantly reduce throughput.Thus, the skilled artisan can adjust the treatment ratio in order toform suitable films in the most efficient manner. In some embodiments apurge process may be applied for purging H₂ before applying a nitrogenplasma treatment in each cycle to reduce or avoid blister formation,while in other embodiments the purge process and or nitrogen plasmatreatment are provided at a reduced frequency in order to increasethroughput while maintaining desired film quality.

Example 5

FIG. 15 shows wet etch rate ratio (WERR) as compared to thermal oxide(TOX) of a silicon nitride films formed on a horizontal (labelled as“Top” in FIG. 15) surface and vertical (labelled as “Side” in FIG. 15)surface of a 3-D feature, versus duration of nitrogen plasma treatment,in seconds, included in one cycle of the silicon nitride formationprocess. The silicon nitride film was grown using a PEALD siliconnitride film deposition process in combination with a nitrogen plasmatreatment. One cycle of the silicon nitride formation process has asequence as follows: 0.3 seconds of a silicon precursor step in whichsilicon precursor, and hydrogen and nitrogen are supplied to thereaction chamber, followed by 0.5 seconds of a purge process in whichnitrogen and hydrogen are supplied to the reaction chamber, followed by3.3 seconds of a plasma nitrogen precursor step in which nitrogen andhydrogen are supplied to the reaction chamber and at a plasma power ofabout 165 W (power density of about 0.11 W/cm³), followed by 10 secondsof a purge process in which nitrogen is supplied to the reactionchamber, followed by a nitrogen plasma treatment in which nitrogen issupplied to the reaction chamber and at a plasma power of about 220 W(about 0.15 W/cm³), and followed by a 10 seconds purge process in whichhydrogen and nitrogen are supplied to the reaction chamber. The siliconnitride film corresponding to FIG. 15 was formed using about 190 cyclesof the sequence, at a temperature 550° C.

As shown in FIG. 15, WERR of horizontal and vertical surfaces can betuned, at least in part, by varying the duration of the nitrogen plasmatreatment in each cycle. FIG. 15 shows that a uniform horizontal surfaceand vertical surface etch rate can be achieved using a nitrogen plasmatreatment having a duration of about 0.9 seconds in the sequence above.

Multi-Step Plasma Exposure

In some embodiments, process for depositing a SiN thin film includes amulti-step plasma exposure. For example, a cycle of a PEALD process fordepositing a SiN thin film may include a first phase which comprisescontacting the substrate with a silicon precursor. In some embodiments,the silicon precursor comprises one or more silicon precursors asdescribed herein. In some embodiments, the silicon precursor comprises achlorine-containing precursor, such as octachlorotrisilane (OCTS).

A PEALD process for depositing SiN thin film includes a second phasewhich comprises contacting the substrate with a nitrogen precursor. Insome embodiments, the second phase of the PEALD process cycle comprisesa multi-step plasma exposure. In some embodiments, the silicon precursorcomprises a chlorine-containing precursor. For example, in someembodiments the silicon precursor may comprise dichlorosilane (DCS),hexachlorodisilane (HCDS) and/or tetrachlorosilane (SiCl₄).

Referring to FIG. 16, an example of a deposition process 1600 is shownfor forming a SiN thin film on a substrate within a reaction chamber.The deposition process 1600 may comprise a PEALD process. In block 1602,the substrate can be exposed to a silicon precursor. For example, thesubstrate may be exposed to octachlorotrisilane (OCTS). In someembodiments, the substrate may be exposed to one or more other siliconprecursors described herein. The substrate may be subsequently exposedto a multi-step plasma exposure. In block 1604, the substrate can beexposed to at least one nitrogen-containing plasma and at least oneother different plasma. The multi-step plasma exposure may compriseexposing the substrate to more than one nitrogen-containing plasma. Forexample, one or more steps of the multi-step plasma exposure maycomprise exposing the substrate to a plasma generated by nitrogen gas(N₂).

In some embodiments, a cycle of a PEALD process comprises blocks 1602and 1604. For example, a first phase of the cycle may comprise block1602 and a second phase of the cycle may comprise block 1604. In someembodiments, the cycle comprising blocks 1602 and 1604 may be repeated1606 a number of times to achieve a SiN film of desired thickness.

In some embodiments, one or more plasma steps of the multi-step plasmaexposure comprises generating a plasma using nitrogen-containing and/orhydrogen-containing gases, and contacting the substrate with the plasma.For example, one or more plasma steps of the multi-step plasma exposuremay include exposing the substrate to a plasma generated using nitrogengas (N₂) and/or hydrogen gas (H₂). In some embodiments, one or more ofthe plasma steps comprises contacting the substrate with plasmasgenerated using both nitrogen gas (N₂) and hydrogen gas (H₂). In someembodiments, one or more of the plasma steps comprises plasmas generatedby using only or substantially only hydrogen gas (H₂).

A multi-step plasma exposure can include two or more steps in which thesubstrate is contacted with a plasma reactant. In some embodiments, amulti-step plasma exposure can include three plasma steps. For example,the multi-step plasma exposure may include two plasma steps eachcomprising exposing the substrate to a plasma generated using bothnitrogen gas (N₂) and hydrogen gas (H₂), and one plasma step comprisingexposing the substrate to a plasma generated using hydrogen gas (H₂).

Referring to FIG. 17, another example of a deposition process 1700 isshown for forming a SiN thin film on a substrate within a reactionchamber. The deposition process 1700 may comprise a PEALD process. Inblock 1702, the substrate can be exposed to a silicon precursor. Forexample, silicon precursor may include octachlorotrisilane (OCTS). Insome embodiments, the substrate may be exposed to one or more othersilicon precursors described herein. The substrate may be subsequentlyexposed to multiple plasmas. In block 1704, the substrate can be exposedto a first plasma generated by using both nitrogen gas (N₂) and hydrogengas (H₂). Subsequently, in block 1706, the substrate can be exposed to asecond plasma generated by using hydrogen gas (H₂). For example, thesecond plasma may be generated using only or substantially only hydrogengas (H₂). In block 1708, the substrate can be exposed to a third plasmagenerated by using both nitrogen gas (N₂) and hydrogen gas (H₂).

In some embodiments, a cycle of a PEALD process comprises blocks 1702,1704, 1706 and 1708. For example, a first phase of the cycle maycomprise block 1702 and a second phase of the cycle may comprise blocks1704, 1706 and 1708. In some embodiments, the cycle comprising blocks1702, 1704, 1706 and 1708 may be repeated 1710 a number of times toachieve a SiN film of desired thickness. In some embodiments, themulti-step plasma exposure is completed prior to exposing the substrateto a non-plasma reactant. In some embodiments, the multi-step plasmaexposure is completed and another non-plasma reactant is not providedinto the reaction chamber prior to contacting the substrate again withthe silicon reactant. For example, the process for depositing the SiNfilm may include completing exposing the substrate to the plasma inblocks 1704, 1706 and 1708 prior to exposing the substrate again to thesilicon precursor in block 1702.

In some embodiments, an interval in which no plasma is generated canfollow a plasma exposure. In some embodiments, the interval can includea step for removing excess reactants and/or reaction byproducts from thereaction chamber. For example, a step for removing excess reactantsand/or reaction byproducts from the vicinity of the substrate may followone or more of the plasma steps in the multi-step plasma exposure. Insome embodiments, the removal step may comprise evacuating the reactionchamber and/or flowing a purge gas through the reaction chamber. In someembodiments, the substrate may be moved to a space free or substantiallyfree of the reactants during the removal step.

In some embodiments, each plasma step can be followed by a purge step.For example, each of exposing the substrate to the first plasma in block1704, exposing the substrate to the second plasma in block 1706, andexposing the substrate to the third plasma in block 1708 may be followedby a purge step. In some embodiments, only some of the plasma steps ofthe multi-step plasma exposure are followed by a purge step. Forexample, a last plasma step of a multi-step plasma exposure may not befollowed by a purge step.

In some embodiments, purge gas of a purge step can comprise an inertgas. For example, a purge gas can comprise a noble gas. In someembodiments, a purge gas can include argon (Ar).

In some embodiments, purge gas of a purge step can comprise one or moregases flowed in a plasma step. For example, purge gas flowed in a purgestep can be selected based on gas used in an immediately succeedingplasma step. In some embodiments, gas flowed in a purge step can be thesame gas used to generate the plasma in an immediately succeeding plasmastep. For example, plasma power may be turned off during the purge stepwhile flow of one or more gases used to generate the plasma in theplasma step preceding the purge step and in the plasma step immediatelyfollowing the purge step can be continued during the purge step, whileone or more gases, if any, not used to generate the plasma in the plasmastep immediately following the purge step can be ramped down and/orturned off during the purge step.

In some embodiments, a duration of each of the plasma steps in amulti-step plasma exposure can be selected to achieve one or moredesired SiN film qualities. In some embodiments, a duration of a plasmastep is longer than that of an immediately succeeding plasma step. Forexample, a first plasma step may have a duration of about 4 seconds toabout 8 seconds, such as about 6 seconds. For example, a second plasmastep may have a duration of about 2 seconds to about 6 seconds, such asabout 4 seconds. For example, a third plasma step may have a duration ofabout 1 second to about 3 seconds, such as about 2 seconds. In someembodiments, a duration of a plasma step may not be longer than that ofan immediately succeeding plasma step. For example, a duration of eachplasma step in a multi-step plasma exposure may have equal orsubstantially equal duration. In some embodiments, a duration of aplasma step can be shorter than that of an immediately succeeding plasmastep.

In some embodiments, the pressure of the reaction chamber during one ormore steps of the multi-step plasma exposure can be about 2 torr toabout 8 torr, including about 2 torr to about 6 torr, or about 2 torr toabout 4 torr.

In some embodiments, a plasma power for one or more steps of themulti-step plasma exposure can be about 50 Watts (W) to about 800 W,such as from about 100 W to about 800 W, about 100 W to about 600 W, andabout 100 W to about 500 W. The plasma power can be selected based onthe silicon precursor used, reaction chamber pressure of the plasma stepand/or the duration of the plasma step. In some embodiments, plasmapower of any one step in a multi-step plasma exposure may be the same asone or more other steps of the multi-step plasma exposure. In someembodiments, plasma power of any one step in a multi-step plasmaexposure may be different from other steps of the multi-step plasmaexposure.

An exemplary sequence for a multi-step plasma exposure in a PEALDprocess for depositing SiN thin films can include three plasma steps andan interval after each plasma step in which the plasma is turned off.Each interval may include a purge step. For example, the multi-stepplasma exposure may include exposing the substrate to a first plasmagenerated by using both nitrogen gas (N₂) and hydrogen gas (H₂). Thefirst plasma step may be followed by an interval in which the plasma isturned off and a first purge step is performed. The first purge step maycomprise flow of hydrogen gas (H₂) and/or one or more other purge gases.The substrate is then exposed to a second plasma generated from onlyhydrogen gas (H₂). The second plasma step may be followed by an intervalin which the plasma is turned off and a second purge step is performed.The second purge step may comprise flow of both nitrogen gas (N₂) andhydrogen gas (H₂), and/or one or more other purge gases. Subsequently,the substrate can be exposed to a third plasma generated by using bothnitrogen gas (N₂) and hydrogen gas (H₂). The third plasma step may befollowed by an interval in which the plasma is turned off and a thirdpurge step is performed. The third purge step may comprise flow of bothnitrogen gas (N₂) and hydrogen gas (H₂) and/or one or more other purgegases. In some embodiments, the third purge step may be omitted.

A flow rate of gases during a purge step and duration of the purge stepmay be selected to facilitate desired removal of excess reactants and/orreaction byproducts. In some embodiments, a flow rate of one or moregases of a purge gas may be the same as a flow rate of the gas during animmediately preceding or immediately succeeding plasma step. In someembodiments, the purge step can have a duration of about 1 second toabout 10 seconds, including about 2 seconds to about 8 seconds. Forexample, a duration of a purge step can have a duration of about 4seconds, or about 6 seconds.

FIG. 18 is a graph showing plasma power and gas flow as a function oftime for an example of a multi-step plasma exposure. The y-axis showsthe amount of reactive gas at the substrate, and the x-axis shows time.FIG. 18 shows an example of a three-step plasma exposure in which thesubstrate is exposed to a hydrogen-containing and nitrogen-containingplasma, followed by a hydrogen-containing plasma, and then followed by ahydrogen-containing and nitrogen-containing plasma. The example shown inFIG. 18 includes plasmas generated using hydrogen gas (H₂) and/ornitrogen gas (N₂), where plasma power is turned on during each of thethree plasma steps, and nitrogen gas (N₂) flow is turned on during thefirst and third plasma steps, while hydrogen gas (H₂) flow is continuedthroughout the multi-step plasma exposure.

As described herein, the graph in FIG. 18 shows three durations in whichplasma is on, or three plasma steps. FIG. 18 shows that each plasma stepmay have a duration shorter than that of the immediately precedingplasma step. For example, the first plasma step starting at time equals0 can have a longer duration than that of the subsequent second plasmastep, and the second plasma step can have a longer duration than that ofthe third plasma step. In some embodiments, each plasma step can have aduration equal to that of other plasma steps. In some embodiments, eachplasma step has a duration shorter than that of an immediately precedingplasma step.

FIG. 18 shows that the first and third plasma steps may comprise flow ofboth hydrogen gas (H₂) and nitrogen gas (N₂), while the second plasmastep may comprise flow of hydrogen gas (H₂). As shown in FIG. 18, flowof hydrogen gas (H₂) may be continued throughout the multi-step plasmaexposure. For example, the flow of hydrogen gas (H₂) can be constant orsubstantially constant throughout the multi-step plasma exposure, whilethe flow of nitrogen gas (N₂) may be ramped up or ramped down during aninterval between plasma steps. For example, as shown in FIG. 18, thenitrogen gas (N₂) may be ramped down, such as a linear ramp, during aninterval between the first and second plasma steps, and may be rampedup, such as a linear ramp, during the interval between the second andthird plasma steps. For example, an interval between plasma steps mayinclude flow of an increasing amount of nitrogen gas (N₂) or adecreasing amount of nitrogen gas (N₂), and a constant or substantiallyconstant flow of hydrogen gas (H₂).

As shown in FIG. 18, the interval between the first plasma step and thesecond plasma step may begin with flow of both hydrogen gas (H₂) andnitrogen gas (N₂), and end with flow of only or substantially onlyhydrogen gas (H₂) as the nitrogen gas (N₂) is ramped down and thenturned off. The nitrogen gas (N₂) flow during the second intervalfollowing the second plasma step may be ramped up. For example, theinterval between the second plasma step and the third plasma step maybegin with ramping up of the flow of nitrogen gas (N₂) and end with flowof both hydrogen gas (H₂) and nitrogen gas (N₂). For example, thenitrogen gas (N₂) flow during the second interval may be ramped up to arate used for the third plasma step.

In some embodiments, the first and third plasma steps of a three-stepplasma exposure may comprise flow of both nitrogen gas (N₂) and hydrogengas (H₂), while the second plasma step may comprise flow of nitrogen gas(N₂). For example, flow of nitrogen gas (N₂) may be continued throughoutthe multi-step plasma exposure. In some embodiments, the flow ofnitrogen gas (N₂) can be constant or substantially constant throughoutthe exposure, while the flow of hydrogen gas (H₂) may be ramped up orramped down during an interval between plasma steps. For example, thehydrogen gas (H₂) may be ramped down, such as a linear ramp, during aninterval between the first and second plasma steps, and may be rampedup, such as a linear ramp, during the interval between the second andthird plasma steps. An interval between plasma steps may include flow ofan increasing amount of hydrogen gas (H₂) or a decreasing amount ofhydrogen gas (H₂), and a constant or substantially constant flow ofnitrogen gas (N₂). For example, the interval between the first plasmastep and the second plasma step may begin with flow of both hydrogen gas(H₂) and nitrogen gas (N₂), and end with flow of only or substantiallyonly nitrogen gas (N₂) as the hydrogen gas (H₂) is ramped down and thenturned off. The hydrogen gas (H₂) flow during the second intervalfollowing the second plasma step may be ramped up. For example, theinterval between the second plasma step and the third plasma step maybegin with ramping up of the flow of hydrogen gas (H₂) and end with flowof both hydrogen gas (H₂) and nitrogen gas (N₂). For example, thehydrogen gas (H₂) flow during the second interval may be ramped up to arate used for the third plasma step.

In some embodiments, a three-step plasma exposure may comprise a firstplasma step comprising flow of hydrogen gas (H₂), a second plasma stepcomprising flow of nitrogen gas (N₂), and a third step comprising flowof both hydrogen gas (H₂) and nitrogen gas (N₂). In some embodiments,nitrogen gas (N₂) may be ramped up and the hydrogen gas (H₂) can beramped down during the interval between the first plasma step and thesecond plasma step, such that only or substantially only nitrogen gas(N₂) is flowed during the second plasma step. The nitrogen gas (N₂) maybe continued during the interval between the second plasma step and thethird plasma step while the hydrogen gas (H₂) is ramped up during theinterval, such that both nitrogen gas (N₂) and hydrogen gas (H₂) aresupplied during the third plasma step. In some embodiments, the flow ofnitrogen gas (N₂) can be kept constant or substantially constant fromthe start of the second plasma step to the end of the third plasma step.In some embodiments, ramping of the flow of the hydrogen gas (H₂) and/ornitrogen gas (N₂) can be a linear ramp.

In some embodiments, a three-step plasma exposure may comprise a firstplasma step comprising flow of both hydrogen gas (H₂) and nitrogen gas(N₂), a second plasma step comprising flow of hydrogen gas (H₂), and athird step comprising flow of nitrogen gas (N₂). In some embodiments,nitrogen gas (N₂) flow can be ramped down during the interval betweenthe first plasma step and the second plasma step, while the flow ofhydrogen gas (H₂) is continued, such that only or substantially onlyhydrogen gas is flowed during the second plasma step. In someembodiments, the flow of hydrogen gas (H₂) is kept constant orsubstantially constant from the start of the first plasma step to theend of the second plasma step. In some embodiments, hydrogen gas (H₂) isramped down during the interval between the second plasma step and thethird plasma step, while nitrogen gas (N₂) is ramped up, such that thethird plasma step flows only or substantially only nitrogen gas (N₂). Insome embodiments, ramping of the flow of nitrogen gas (N₂) and/orhydrogen gas (H₂) may be a linear ramp.

In some embodiments, a PEALD process for depositing a SiN thin filmcomprising a multi-step plasma exposure can be followed by one or moreother plasma treatments as described above.

Example Film Characteristics of a SiN Film Deposited Using a Multi-StepPlasma Exposure

FIG. 19A is table showing characteristics of two SiN thin films. Thetable in FIG. 19A lists the growth rate, in angstroms per cycle(Å/cycle), the refractive index, and the wet etch rate (WER), innanometers per minute (nm/min), of each of the SiN films. The table alsolists the wet etch rate ratio (WERR) comparing wet etch rate of each ofthe SiN films to that of thermal oxide (TOX). The wet etch rates and wetetch rate ratios shown in the table of FIG. 19A were measured afterexposing the films to 0.5 weight % hydrofluoric acid (HF) solution(dilute HF, or dHF).

The SiN film shown in the first row of the table in FIG. 19A was formedusing a PEALD process having a process temperature of about 120° C. Acycle of the PEALD process included a first phase in which the substratewas contacted with a silicon precursor comprising octachlorotrisilane(OCTS). The second phase of the PEALD process cycle included a singleplasma step in which the substrate was contacted with a plasma generatedusing both nitrogen gas (N₂) and hydrogen gas (H₂).

The SiN film described in the second row of the table in FIG. 19A wasformed using a PEALD process having a process temperature of about 120°C. A cycle of the PEALD process included a first phase in which thesubstrate was contacted with a silicon precursor comprisingoctachlorotrisilane (OCTS). The second phase of the PEALD process cycleincluded a multi-step plasma exposure in which the substrate was exposedto three plasma steps. The sequence of the multi-step plasma exposureused to form the SiN film shown in the second row of the table isprovided in the table of FIG. 19B. As shown in FIG. 19B, the secondphase of the PEALD process included a first plasma step having aduration of about 6 seconds in which the plasma was generated using bothnitrogen gas (N₂) and hydrogen gas (H₂). The first plasma step wasfollowed by a first purge step having a duration of about 4 seconds. Theplasma was turned off during the first purge step and the first purgestep included flow of hydrogen gas (H₂). Subsequently, the substrate wasexposed to a second plasma for a duration of about 4 seconds, where thesecond plasma was generated using hydrogen gas (H₂). Then a second purgestep having a duration of about 4 seconds was performed, where thesecond purge step comprised flowing of nitrogen gas (N₂) and hydrogengas (H₂). The second purge step was followed by a third plasma step. Thethird plasma step had a duration of about 2 seconds, in which thesubstrate was exposed to a plasma generated using nitrogen gas (N₂) andhydrogen gas (H₂). The complete cycle of the PEALD process was repeatedabout 500 times to achieve a SiN film having a thickness of about 37nanometers.

As shown in the table of FIG. 19A, SiN film growth rates per cycle ofthe two PEALD cycles and the refractive indices of the two SiN filmswere similar. The PEALD process for forming the SiN film shown in thefirst row demonstrated a film growth rate of about 0.73 Å/cycle and thedeposited SiN film demonstrated a refractive index of about 1.78. ThePEALD process for forming the SiN film shown in the second rowdemonstrated a film growth rate of about 0.74 Å/cycle and the depositedSiN film demonstrated a refractive index of about 1.80. Meanwhile, theSiN film shown in the second row of the table in FIG. 19A and depositedusing the multi-step plasma exposure demonstrated a significantly lowerwet etch rate in dHF (0.5%), as compared to that of the SiN film shownin the first row. As shown in the table of FIG. 19A, the wet etch rateof the SiN film in the second row, formed using the multi-step plasmaexposure, was about half that of the SiN film shown in the first row.The table in FIG. 19A also shows that the wet etch rate ratio of the SiNformed using a multi-step plasma exposure was about half that of the SiNfilm in the first row, formed without using the multi-step plasmaexposure.

Without being limited by any particular theory or mode of operation, aPEALD process for forming a SiN thin film comprising a multi-step plasmaexposure can facilitate formation of SiN films having desired wet etchrates, including desired wet etch rates in 0.5 weight % HF solution. Forexample, a PEALD process comprising a multi-step plasma exposure mayfacilitate formation of SiN films having desired wet etch rates, whileproviding desired film deposition rates and/or films having otherdesired film characteristics, such as film refractive indices.

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. The described features, structures,characteristics and precursors can be combined in any suitable manner.Therefore, it should be clearly understood that the forms of the presentinvention are illustrative only and are not intended to limit the scopeof the present invention. All modifications and changes are intended tofall within the scope of the invention, as defined by the appendedclaims.

What is claimed is:
 1. A method of forming a SiN thin film on a surfaceof a substrate in a reaction space comprising: contacting the substratewith a silicon precursor comprising SiI₂H₂ to provide a first siliconspecies adsorbed on the surface of the substrate; contacting thesubstrate comprising the first silicon species adsorbed on the surfacewith a first plasma comprising activated hydrogen species therebyforming SiN on the substrate; and contacting the substrate comprisingSiN with a second plasma formed from a nitrogen containing gas, whereinthe first plasma is generated using a first power and the second plasmais generated using a second power that is different from the firstpower.
 2. The method of claim 1, wherein the first plasma comprises atleast one of hydrogen, hydrogen atoms, hydrogen plasma, hydrogenradicals, N* radicals, NH* radicals and NH₂* radicals.
 3. The method ofclaim 1, wherein the second plasma is formed from a nitrogen containinggas that is substantially free of hydrogen-containing species.
 4. Themethod of claim 1, wherein the second power is greater than the firstpower.
 5. The method of claim 4, wherein the second power is up to 900%of the first power.
 6. The method of claim 1, wherein the second poweris less than the first power.
 7. The method of claim 1, wherein thesecond power is between 50% and 100% of the first power.
 8. The methodof claim 1, wherein the first power is from 50 W to 600 W.
 9. The methodof claim 1, wherein the second power is from 100 W to 1000 W.
 10. Themethod of claim 1, wherein the first plasma has a plasma energy of lessthan 2500 W*s.
 11. The method of claim 1, wherein the second plasma hasa power density of about 0.07 W/Cm³ to about 70 W/cm³.
 12. The method ofclaim 1, wherein the substrate is contacted with the first plasma for afirst duration and contacted with the second plasma for a secondduration that is less than the first duration.
 13. The method of claim12, wherein the second duration is 5% to 75% of the first duration. 14.The method of claim 1, further comprising repeating contacting thesubstrate with the silicon precursor comprising SiI₂H₂ and contactingthe substrate with the first plasma two or more times prior tocontacting the substrate with the second plasma.
 15. The method of claim14, wherein the substrate is contacted with the second plasma after atleast 25 repetitions.
 16. The method of claim 14, wherein a totalduration during which the substrate is contacted with the first plasmais greater than or equal to a total duration during which the substrateis contacted with the second plasma.
 17. The method of claim 1, furthercomprising exposing the substrate to a third plasma different from atleast one of the first plasma and the second plasma.
 18. The method ofclaim 1, wherein the SiN thin film is formed on a three-dimensionalstructure comprising a sidewall and a top region and wherein a ratio ofa wet etch rate (WER) of the SiN thin film on the sidewall to a wet etchrate (WER) of the SiN thin film on the top region is from 0.75 to 1.5 in0.5% dHF.
 19. The method of claim 1, wherein an etch rate ratio of anetch rate of the SiN thin film to an etch rate of a thermal siliconoxide film is less than 0.5 in 0.5% aqueous HF.